Unit 1
Pure Substances
and Mixtures
Unit I Overview
Getting Started: What Are Things Made Of?
I. I
Inquiry Investigation: Classifying Substances
1.2
Pure Substances and Mixtures
I .3
Inquiry Investigation: Filtering Mechanical Mixtures
I .4
I .5
Inquiry Investigation: Are All Solvents Alike?
How Do Solutions Form?
I .6
Case Study: Flaky Baking
I. 7
I .8
Inquiry Investigation: The Rate of Dissolving
Saturated or Unsaturated?
I .9
Inquiry Investigation: Solubility and Saturation
I. IO
I. I I
Inquiry Investigation: Separating Mixtures
Using Gases
I. I 2
Products from Raw Materials
l.I3
Design Investigation: Concrete for Construction
1. I 4
l.I5
Inquiry Investigation: Solvents in the Laundry
The Importance of Water
I.I6
Testing Water Quality
l.I 7
Inquiry Investigation: How Hard Is the Water?
l.I8
Household Hazardous Waste
l.I9
Explore an Issue: Cleaning Up Our Water
I .20
l.2I
Career Profile: Wetlands Preservation
Water Additives
Design Challenge: Design and Build a System That
Separates or Purifies Materials
Unit I Summary
Unit I Review
Sustainability Concerns
M
atter is all around us: the air we breathe, the lakes and
oceans, and Earth itself are all made of matter. To
manufacture things or make them useful to us, we work
with matter in all sorts of ways:we purify matter to obtain
metals, mix up other types of matter to make foods or drinks, and we
separate manufactured items to recycle the parts. But how do we know
which substances will mix well for a particular purpose? Can we classify
matter in a way that will help us make predictions?
Classifying Matter
Using Matter to Make Products
Matter_can be classified into many different
categories. This helps us make sense of the
thousands of different substances around us.
The products that we use in our everyday lives
make use of the physical properties of the
substances they are made from.
The use of large amounts of raw materials
from the Earth to manufacture a wide range of
products has an impact on the environment,
the economy, and our health. Our
environment is affected by manufacturing and
agricultural processes. It needs to be protected
by regulations and public awareness programs.
You will be able to ...
demonstrate your learning by
completing a Design Challenge.
A System That Separates or Purifies
Materials
Recycling substances and
products, both liquid and solid, is
an important way of preserving
Earth's resources and reducing
garbage. However, recycling and
separating substances also
requires many types of
technology.
In this unit you will be able to
design and build:
II
You will be able to:
• identify the sources and
characteristics of pollutants
that result from manufacturing
and chemical fertilizers
• distinguish between pure substances and
mixtures
• describe the effect of some
toxic solvents on the environment, and
regulations that ensure their safe use and
disposal
• investigate different methods of separating
the components of mixtures
• identify different types of waste present in
the community and methods of disposal
You will be able to:
• use the particle theory to explain how
substances dissolve
• conduct experiments to determine the
factors that affect the rate at which
substances dissolve
• describe the difference between saturated
and unsaturated solutions
You will be able to:
• distinguish between raw materials and
processed materials
• evaluate the quality of water from different
sources by performing simple tests
II
II
A Water Purification System
Design and build a model
of a filtering system that
removes solid particles
from water.
A Recycling System for
Plastic, Glass, Metal, and
Paper
Design and build a model
in which plastic, glass,
metal, and paper items are
separated from each other.
A Soil and Gravel
Mechanical Separator
Design and build a model
that efficiently separates
soil and rocks into three
different sizes.
• describe how raw materials are collected
and processed to produce products
To start your Design Challenge,
see page 62.
• identify a variety of manufactured products
made from mixtures and explain their
functions
Record your thoughts and design
ideas for the Challenge when you
see
• recognize that solutions in manufactured
products can exist as solids, liquids, and
gases
12
Unit 1
Pure Substances and Mixtures
13
What Are Things Made Of?
O We
can see and feel most types
of matter. We can also describe
them in many different waysfor example, soft, hard, shiny,
colourful, brittle, liquid, solid.
Some things, like air, we cannot see
or taste. Why is it important to have a
way to classifythings? Which
classification system is best? Does one
classificationwork for everything?
e
The raw materials we use to
make products all come
from the Earth. Some, like
our food, we grow, Others,
like metals and other
minerals, we mine. And
when we don't want
something anymore, or it
breaks, we throw it away.
Both retrieving substances
from the Earth and
throwing things into
landfills have an effect on
the environment. How can
we lessen this effect and
create a balance between
environmental concerns,
health concerns, and
economic concerns?
Reflecting
Think about the questions in
0.@. €).
What other questions do you have
about mixtures? As you progress
through this unit, reflect on your
answers and revise them based on
what you have learned.
Classifying Candy
G To
make products, we mix raw
materials together in combinations
that may require heating, freezing,
stirring, melting, hardening, or
dissolving. Through a series of
processes, we end up with the items
that we buy and use every day. How do
we know which materials mix best to
give us the product we want? How do
we decide which is the best process to
use when manufacturing a product?
14
nit I
Examine some chocolate candy bars and
organize them into categories.
3. Do you think chocolate is pure? Why
or why not?
•
•
Using a dinner knife, cut each candy
bar into pieces.
Organize the candy bars into
categories.
1. Does each candy bar look the same
throughout, or can you see other
substances mixed in?
4. Did your group choose the same
categories as other groups? Could you
improve your system of categories?
2. What makes a bar that contains only
5. What considerations do you need to
make when designing a classification
system?
chocolate different from other
chocolate bars?
Pure Substances and Mixtures
15
,
1. ~ Inquiry Investigation
I
SKILLS MENU
o Questioning
o Hypothesizing
• Conducting
• Recording
• Analyzing
• Communicating
OPlanning
Making Connections
Classifying Substances
1. Using your classification
system, describe how you
would categorize the
following:
Take a look around you. Everything is made of matter-including your
own body, the products you use, Earth, and the universe (Figure 1).
Matter is anything that has mass and takes up space. Matter is made up
of many different kinds of substances. Some of these substances are
similar to each other, and some have obvious differences. It is these
similarities and differences that allow us to classifythem.
Materials
•
•
•
•
Question
Which similarities and differences among substances can be used to
organize, or classify,matter into different types?
Hypothesis
If we choose certain properties, then we can classifyall forms of matter.
Procedure
Part 1: Observing Properties of Matter
•
•
•
•
apron
rubber glo:ves
safety goggles
substance samples. e.q..
chalk, tennis ball. iron
nails, salt, powdered
drink mix, stainless steel
nuts and bolts, air, water,
celery, carrot sticks,
mixed nuts. flour. alcohol,
sand. charcoal
magnifier
test tube
50-ml beaker
paper
(a) cheese and pepperoni
pizza
(b) orange juice
(c) smoke
(d) wood
Exploring
UPMll
2. In separate containers, mix
water with cocoa, gelatin
powder. and ground coffee.
Record your observations,
and classify each mixture
according to your system.
Matter includes all things that have mass and take up space.
There are many useful ways to categorize matter.
Reflecting
Part 2: Observing Properties of Mixed Samples
3. Speculate why it is helpful to
classify matter.
Analysis
m Analyzeyour results by
answering these questions.
(a) Compare your classification
system with those of your
classmates.
DMake an observation table El Place a spoonful of each
like the one below.
@) • Examine the samples that
are solid, hard objects.
~ (a) List all the properties
you observe in your
table.
of the powdered solids
onto a separate piece of
paper.
• Use a magnifier to
carefully examine each
sample.
~ (a) Record all the
properties you observe
in your table.
Observations
Sample
Observations
Observations after
mixing with water
Observations after
mixing with other
solids
?
?
?
?
?
?
?
?
16
Unit 1
IJ Observe the liquid and
gas samples ( do not
remove these samples
from their containers).
~ ( a) Record your
observations in your
table.
(b) Based on all your
observations, classify
the different types of
matter into groups.
IJ Place a spoonful of one of El Select two of the
the powdered solids into a
test tube. Add water to fill
half the test tube.
• Put your thumb over the
end of the test tube and
invert it. Hold it away
from your body and
shake.
~ (a) Record your
observations in the
third column of your
table.
• Wash out the test tube
and repeat step 4 with
each of the powdered
solids.
SKILLS HANDBOOK: (so) Creating Data Tables
powdered substances and
mix together a spoonful
of each in a beak.er.
~ (a) Record your
observations in your
table.
(b) Do all of the mixtures
you've made fit in your
original classification
system?If not, change
your system so all of
the forms of matter
you've observed can
be classified.
(b) What are the similarities and
differences among the
different classification
systems?
( c) Create a flowchart of your
classification system.
O)sign Challenge
Think about how you could
separate each mixture you made
in Part 2 of this investigation so
that you could have the original
substances you started with. Rate
each mixture as "easy to
separate," "difficult to separate,"
or "probably cannot be
separated." Explain why you rated
each mixture as you did.
Pure Substances and Mixtures
17
'
.
1.2
WB'iiil
I
Table sugar is obtained by a refining
process in which the sugar from sugar
beets or sugar cane (raw material) is
separated from the fibre and other parts of
the plant. Aluminum comes from bauxite
(raw material). a type of rock that contains
aluminum mixed up with other minerals.
Pure Substances and Mixtures
In the previous investigation you looked at different substances. But
why is each substance different from other substances? Why does each
substance have its own properties?
The Particle Theory
To answer these questions
we need to look at the
particle theory. The particle
theory, developed over
many centuries, explains
that matter is made up of
tiny particles with spaces
between them (Figure 1).
Particles are alwaysmoving.
The more energy they have,
the faster they move. The
particle theory also explains
that the tiny particles in
matter are attracted to each
other (Figure 2). This
theor_yhas been useful in
explaining some
observations about the
behaviour of matter.
iiiMiiJ
Solid
In a solid, the particles are
close together and locked into
a pattern. They can move, but
only back and forth a little.
Attractive forces hold the
particles toqether,
Unit 1
bauxite
Different Particles, Different
Substances
aluminum foil
According to the particle theory, there are
many different kinds of particles. The
differences between the particles cause the
substances that contain them to have different
properties.
Pure Substances
A pure substance contains only one kind of
particle throughout. There are many pure
substances, but only a few can actually be
found in nature. We often think of our
drinking water as being pure, but this water
has chemicals in it to remove bacteria, so it is
actually made up of several pure substances. In
nature, pure substances tend to mix together.
There are exceptions; for example, diamonds
are pure. They are formed deep in the mantle
of Earth's crust, but they are rarely found.
Almost all of the pure substances we
encounter in our lives have been made pure
by human beings. Aluminum foil is pure, and
so is table sugar. To obtain these substances in ·
a pure form, we take the raw material that
contains them, and separate out the substance
we want, as shown in Figure 3. All samples of
pure substances have the same properties
whether the sample is large or s1:1all.
Liquid
In a liquid, the particles are
slightly farther apart. Because
the particles are farther apart,
the attractive forces are
weaker. They are able to slide
past one another.
18
table sugar
Gas
In a gas, the particles are far
apart. The particles can move
in 'anv direction because the
attractive forces are weakest.
iii\Mii•
Mixtures
Almost all of the natural substances, as well as
human-made and manufactured products, in
the world are mixtures of pure substances. A
mixture contains two or more pure substances,
as shown in Figure 4. Mixtures can be any
combination of solids, liquids, and gases. For
example, soft drinks are a mixture that includes
liquid water, solid sugar, and carbon dioxide
gas. Bread is a mixture of yeast, flour, sugar,
water, air, and other chemicals.
Most substances you will come in contact with are mixtures.
Mixtures contain at least two pure substances.
pure substance
mixture
pure substance
Is Tap Water a Solution?
•
Clean two glass containers or watch
glasses, ensuring that there are no spots
on them.
•
Mark one container T (for tap water)
and the other D (for distilled water)'.
•
With a clean medicine dropper, add 5
drops of tap water to the container
marked T, and 5 drops of distilled water
to the container marked D.
•
Place the containers near a sunny
window or a heater, and let them stand
until the water evaporates.
•
Hold the containers up to the light.
1. What do you notice about each
container?
2. Based on your observations, is tap water
a solution? Explain.
3. How would you classifythe distilled
water? Explain.
4. Do you think evaporation is a reliable
method for separating a dissolved solid
from all liquid solutions? Why or why
not?
Pure Substancesand Mixtures
19
liMMM
Classification of Matter
copper
zinc
matter
AA f A/
A A
A
AA
example.
mechanical mixture
(heterogeneous)
pure substance
mechanical mixture
Ulil'Mii
Pure substances mix to form mechanical mixtures or solutions.
In a solution, the particles of the pure substances are mixed
evenly so that neither original substance is visible. In a
mechanical mixture, the substances do not mix evenly. Both
substances are clearly visible.
Heterogeneous and
Homogeneous Mixtures
In many mixtures, like concrete or granola,
you can clearly see separate pieces in the
mixture. Each spoonful of granola is different.
If you take up a spoonful of wet concrete, it
may or may not contain a pebble. This type of
mixture is called a heterogeneous mixture
(heterogeneous means "different kinds"),
solutions
(homogeneous)
because two or more substances can be seen
and felt. If you take a small sample from such
a mixture, it may have different properties
from another sample. Another name for a
heterogeneous mixture is a mechanical ·
mixture ( see Figure 5) .
In a homogeneous mixture (homogenous
means "same kind"), the particles of the pure
substances mix together so completely that
the mixture looks and feels as though it is
made of only one substance. No matter where
you sample it, or how small the sample is, the
properties of this mixture are alwaysthe same.
Steel, composed of iron, oxygen, and carbon,
is a homogeneous mixture. No matter where
you cut a steel bar, it alwayslooks the same.
When you mix a small amount of salt with
water you create a homogeneous mixture.
Another name for a homogeneous mixture is
a solution. We can classifymatter based on its
observable properties (see Table 1).
Mechanical Mixtures and Solutions from the Refrigerator
•
Make a jelly dessert in a clear glass bowl
following the package directions. When
the jelly has set, observe it closely.
1. Is the jelly transparent?
2. Can you see more than one type of
particle?
3. How would you classifyit?
4. Is the jelly a solution?
•
Try shining a flashlight through the
bowl, so any fine particles will become
visible.
5. What do you think now? Would you
change your classification? State reasons.
20
Unit 1
(b) What is a mixture? Give an
solution
pure substance
pure substance
1. (a) What is a pure substance?
Give an example.
pure substances
mixtures
Understanding Concepts
•
Add a tablespoon of chocolate syrup to
a glass of water and stir until the syrup
and water are thoroughly mixed.
6. Is the mixture homogeneous
(a solution) or heterogeneous
(a mechanical mixture)?
•
Let the mixture stand for a while, then
observe it again.
7. What do you notice?
8. Make a list of other mixtures that have
similar properties to chocolate syrup
and water.
2. Identify the solute and the solvent
ili'iii:j
in the picture below.
Brass, a decorative metal, is a solid solution in which a small amount of
zinc (the solute) is dissolved in copper (the solvent) while it-is molten
hot. The zinc makes the brass harder than pure copper.
More About Solutions
In a solution, one substance has mixed
completely, or dissolved, into another.
Solutions can be solid, liquid, or gas. Steel, a
solid solution, is made when oxygen (a gas)
and carbon (a solid) dissolve into the main
substance, iron. The substances that dissolve
(in the case of steel, oxygen and carbon) are
called the solutes. The substance into which
they dissolve (iron) is called the solvent. Brass
is another solid solution. The solvent in brass
is copper, and the solute is zinc, as you can
see in Figure 6.
Air, a solution of gases, consists mostly of
nitrogen gas (the solvent). The gases dissolved
in it include oxygen, argon, and carbon
dioxide (the solutes).
Liquid solutions are formed when a solid,
a liquid, or a gas dissolvesin a liquid. For
example, apple juice is a solution of sugar and
minerals (the solutes) dissolved in water (the
solvent). The oceans are a solution of many
different salts dissolved in water. Another
liquid solution is vinegar. Vinegar, used on
French fries and salads, and for cleaning
stains, is a solution that consists mostly of
water (the solvent) and a small amount of
liquid acetic acid ( the solute).
Liquid solutions may also include dissolved
gases. Pop is a sweet solution that is mostly
water (the solvent), with both solid sugar and
carbon dioxide gas (the solutes) dissolved in
it. All solutions are homogeneous, so they
look the same throughout, but liquid and gas
solutions are also transparent (you can see
through them). They may have a colour,
however, as the solutions apple juice and
tea do.
3. Describe in your own words the
difference between a mechanical
mixture and a solution. Include the
terms homogeneous and
heterogeneous in your answer.
4. Which of the following is a
solution, and which is a mechanical
mixture? Explain the reason for
your choice.
(a) wood
(c) tap water
(b) orange juice
(d) loonie coin
Making Connections
5. Give an example of each of the
following types of solutions (not
including those already mentioned
in this section):
(a) a liquid in a liquid
(b) a solid in a solid
(c) a solid in a liquid
6. Make a chart and list 10 liquids
found at home. Examine the
contents by reading the labels on
the containers.
(a) On your chart identify the
liquids that meet the definition
of a solution.
(b) For each solution, list the
solvent and the solute(s) on
your chart.
Are the mixtures you must
separate for your Challenge
mechanical mixtures or solutions?
Pure Substances and Mixtures
21
SKILLS MENU
O Questioning
• Hypothesizing
O Planning
• Conducting
e Recording
• Analyzing
• Communicating
Making Connections
Filtering Mechanical Mixtures
Since most substances are mixtures, there are many situations when we
want to separate the parts of a mixture. For example, you don't want to
drink water that contains a mixture of soil, tiny plants and animals, and
dissolved chemicals. Several techniques are available to separate
mixtures. The water we drink is made safe by treating it at a water
treatment plant to take out the impurities. Filtration is a technique that
is frequently used in water treatment to separate particles from a
mechanical mixture. Depending on the size of the particles that are
being separated, the size of the mesh in the filter can be large, as in a
screen, or very small, as in filter paper.
Question
Will filter paper separate all solid particles from a liquid mechanical
mixture?
Hypothesis
-Write a hypothesis for this investigation.
1. Describe how you could use
kitchen utensils to separate
each of the following
mechanical mixtures:
Materials
•
•
•
•
•
•
•
•
•
•
•
•
apron
safety goggles
filter paper
milk
water
ground pepper
flour
support stand
ring clamp
funnel
350-ml beakers
water bottle with squirt
top
• stirring rod
Experimental Design
You will test whether filter paper can be used with three different
mechanical mixtures.
(a) sugar, toothpicks, and
uncooked rice
lb) chocolate chips,
chocolate-covered
peanuts, and small
marshmallows
Exploring
WMll
Water taken from a fast-moving
stream will contain small particles of
soil and microscopic living things.
Filters can help to remove many of
these particles from water. But
even if water looks clear, does that
mean it is safe to drink?
D)sign Challenge
Could you use a filter for
separating materials in your
Challenge? If so, what size
must the mesh be? What
forces will the filter have to
resist? What materials should
the filter be made of?
Procedure
2. Birdseed contains several
types of seeds. With 250 ml
of birdseed, design a
procedure with your group to
find out the amount of each
type of seed, in units of mass
or volume. With your
teacher's approval, try it.
3. The screens on your
windows and doors are filters
that separate insects such as
flies and mosquitoes from
the air. Make a chart and list
the different types of filters
that might be found at home,
at school, or in a car, as well
as their purpose.
Analysis
II Analyzeyour results by
answering these questions.
fI Set up a support stand,
ring clamp, funnel, and
beaker as shown above.
A
V'
22
Wash your hands
with soap and water
after you complete
this investigation.
II Fold a piece of filter
paper in half twice and
shape it into a cone.
• Place the filter paper in
the funnel.
• Squirt the paper cone
with water so that it stays
in place in the funnel.
El Measure 25 mL of milk
into a graduated cylinder.
• Pour the milk into the
funnel.
• Wait a few moments for
the liquid to pass through.
(a) Observe the filtered
liquid in the beaker.
How does it compare
with the milk?
(b) Is there any residue
left on the filter
paper?
Unit 1
El Remove the used filter
paper and rinse the
funnel with water.
• Measure out 25 mL of
water in a graduated
cylinder and pour it into a
beaker.
• Mix 2.5 mL of flour into
the beaker and stir.
• Repeat steps 2 to 4 using
this mixture instead of
milk.
SKILLS HANDBOOK:
Ii) Measure out 25 mL of
water in a graduated
cylinder and pour it into a
beaker.
• Mix 2.5 mL of pepper into
the beaker and stir.
• Repeat steps 2 to 4 using
this mixture.
® Predicting and Hypothesizing
@ Designing an Inquiry Investigation
(a) What evidence do you
have that each of the
liquids in this
investigation is a
mechanical mixture?
(b) What feature of the filter
would you change to
completely separate the
substances in each of the
mechanical mixtures?
(c) Based on your
observations, was your
hypothesis correct?
Pure Substances and Mixtures
23
'
1.4 Inquiry·
lnvestiqation
•
-~!.:.o e
U
'd.J.-
G Conducting
O Analyzing
• Recording
• Communicating
Question
Are the solvents water and ethanol alike?
Hypothesis
D Read the Experimental Design and write a hypothesis that this
investigation will attempt to prove.
You will mix a variety of substances
into both water and ethanol, and
observe which ones form solutions,
and which form mechanical mixtures.
V
.,...
L ,1•
r
I
"'
1. Dry-cleaning machines use a
liquid to dissolve and remove
grease, but the liquid is
expensive. What are some
possible ways of reducing
this expense?
Ufolilil
As you learned earlier, a solvent is a substance in which other
substances, or solutes, are dissolved. Centuries ago, scientists spent
much time in their laboratories experimenting with solvents. They were
hoping to find one solvent that dissolved everything. Instead, they
found that solvents have different abilities to dissolve different
substances (Figure 1).
A
~
,'Ai
Making Connections
Are All Solvents Alike?
Experimental Design
..,
-=- '•"}
SKILLS MENU
O Questioning
• Hypothesizing
OPlanning
Ethanol is toxic and flammable.
Do not allow it to come in
contact with your skin; do not
allow an open flame in the
room.
Materials
•
•
•
•
•
•
•
•
•
apron
gloves
safety goggles
water
ethanol
test tubes
rubber stopper
flashlight
salt. sugar. flour. rice,
bath salts. butter. candle
wax. drink crystals
Different solvents
have different
properties. How will
this affect their ability
to dissolve various
solutes?
2. Imagine that you have
accidentally spilled perfume
into a bath. The perfume
contains a rare, expensive oil,
which you can see floating on
the bath water. What steps
could you take to recover as
much of the oil as possible?
Exploring
3. Oil spills that occur near
shorelines are often cleaned
up with the help of powerful
detergents. How do you think
this works?
Reflecting
4. How would you classify the
mixtures in this investigation?
Which mixtures are possible
to separate using the
filtration technique from
Investigation 1.3 or the
evaporation technique from
the Try This in 1.2?
Procedure
n
fJ Pour 15 mL of water into
Analysis
II Analyzeyour results by
II Place the rubber
stopper
in the test tube and shake
it awayfrom your body
while you count to 5.
• Let the test tube stand for
a minute or so.
a clean, dry test tube.
• Add a pinch of salt.
~ (a) What happens in the
test tube? Record your
observations.
~
~
24
Unit 1
(a) Has any change
occurred in the test
tube? Record your
observations.
(b) Record whether the
test tube contains a
mechanical mixture or
a solution.
llJ Repeat steps 2 and 3 with
each of the substances you
are given, using water as
the solvent. If you are not
sure if a mixture is clear
or cloudy, try shining a
flashlight through it, so
any fine particles will
become visible.
El Dispose of the contents of
the first set of test tubes,
as directed by your
teacher. Rinse the tubes
and shake out any water.
m Repeat steps 2, 3, and 4
using ethanol instead of
water to test each of the
solids you.are given.
~ (a) Record your
observations.
(a) Which mixtures have
fine particles
suspended in the
water? Are they
solutions or
mechanical mixtures?
answering these questions.
(a) Which substances formed
a solution when mixed
with:
• water?
• ethanol?
(b) Which substances formed
a mechanical mixture
when mixed with:
• water?
• ethanol?
(c) Write a summary
paragraph to support or
disagree with your
hypothesis.
SKILLS HANDBOOK:
@ Predicting and Hypothesizing
Pure Substances and Mixtures
25
I,.
1.5
Drink particle
Understanding Concepts
1. Draw and label a series of
How Do Solutions Form?
@ diagrams to
show the sequence of
events that occurs when a sugar
cube is dropped into water.
Why do some substances mix easily to form
solutions, while others do not mix at all? For
instance, in the previous investigation you
observed that salt mixes readily with water to
form a solution, yet does not form a solution
with ethanol.
·
I
I
,
I
I
The Particle Theory and Drink
Crystals
To answer this question we need to revisit the
particle theory. When you make a drink, you
may mix together drink crystals and water.
Each solid drink crystal contains billions of
small particles that are tightly attracted to
each other. As long as they are in their
package, they will stay in their crystal form.
However,when the drink crystals are mixed
into water, the particles at the surface of the
crystal are attracted to water particles, as
shown in Figure 1. If the attraction to the
water particles is at least as strong as to other
drink crystal particles, some of the particles
on the surface of the crystal will break their
connections to the rest of the crystal and float
off into the water. This process continues until
the drink crystals break apart and mix
completely, or dissolve, in the water.
If the particles of the solute are not
attracted to the particles of the solvent, the
two substances generally cannot form a
solution.
How Do Solute and Solvent
Particles Fit Together?
,
,,
0(1(10
(l(IQ(I
L:.
.._,.
(I '"' (I
~
~
,
I
, ''
'
explain how a solute dissolves
in a solvent?
(b) Based on the particle theory,
why would a substance
dissolve in one solvent, but
not in another?
.
Making Connections
2. Imagine that you could take all the
students in your class to the gym
to help you illustrate the process
of dissolving. What instructions
might you give them?
,'
-
~""" ~
'-~~~~~~~~~~~~~~--'
,','
,,
,,
I
,, '
,'
.••••.
,,
,,
,
,,
I
'
(a) How does the particle theory
,,
/
,
,,
3. Using what you know about
particles, predict two ways you
could shorten the time it takes to
dissolve sugar in a drink. Explain
your predictions.
/
I
I
WM iii
----------------
A Model for a Solution
You can make a model of the solute and
solvent particles in a solution. The
advantage of a model is that you can
observe a process that you ordinarily
wouldn't be able to see.
50 ml sand + 50 ml marbles
? ml
•
Half-filla clear container with marbles
and mark the level with a grease
pencil or marker. Then half-fill a
second, identical container with sand.
1. Predict the total volume that will
result when the marbles and sand are
combined.
•
Carefully pour the sand into the
container of marbles and shake gently.
2. How accurate was your prediction of
the volume of the mixture? Explain.
A solution occurs when all the drink particles
break apart from the crystal, and mix completely
with the water particles.
3. How is the container of sand and
marbles like a solution?
-, I
Unit 1
4. Make a general statement relating
the sizes of particles of
substances and their combined
volume when they are mixed.
~
When the tiny particles of a solute are
dissolved, or mixed completely, with the
particles of a solvent such as water, the
solute particles fit in the spaces between
the solvent particles.
26
Reflecting
Dissolving occurs when the
attraction of a drink particle for a
water particle is at least as
strong as the attraction to the
other drink particles.
SKILLS HANDBOOK:
@ Scientific & Technical
Drawing
Pure Substances and Mixtures
27
i·
1..6
Case Study
I
iitMiil
A flaky crust is all
in the mix.
Flaky Baking
Understanding Concepts
1. Describe in your own words the
role of each of the following
dough ingredients:
(a) flour
In baking, flour, fat, and water are mixed together. So why is making good pastry
so difficult?The behaviour of matter is affected not only by the properties of the
substance, but also by external factors such as temperature and humidity.
The main ingredients don't seem very mysterious (Figure 1), but getting
the right mixture of these common substances remains a mystery that takes
apprentice bakers years to master.
(b) fat
(cl water
(d) salt
(e) baking powder
2. (a) What is gluten?
Flour and Water
The secret to flaky pastry lies in knowing how
the three main ingredients work together.
Flour contains many substances, including
minerals and other nutrients, but the protein
in the flour is pastry's "backbone." When
flour mixes with water, the protein forms a
substance called gluten, which gives dough
strength and elasticity.But "sturdy" and
"elastic" are not words you want to hear after
critics have taken a bite of your pastry. What is
needed is just enough strength to hold the
crust together. That is why most of the steps
and ingredients in a pastry recipe are
designed to minimize gluten development.
For example, pie crust is less likely to be
tough if cake and pastry flour is used, instead
of bread flour. Cake and pastry flour is 7%
protein; bread flour is 12% protein.
(a) Explain how bread flour would make
tougher pastry.
Fat and Flour
Liquid fat and oils do not form a water
solution. Instead they will form a layer floating
on water. If you force them to mix they will
form a mechanical mixture, with fat forming
globules in the water. It is this property that
enables fat to play a major role in pastry by
''waterproofing" flour particles. Small globules
of vegetable shortening, lard, or butter can
surround flour particles. Whenever water
cannot reach the flour, gluten cannot form.
When there is enough fat in the mixture,
gluten forms only short strands.
(b) Why is the term "shortening" often used
instead of "fat"?
28
Unit 1
(c) Why is it a good idea to add fat to the
flour before adding water?
( d) What kind of mixture is dough? Explain.
Cold and Flaky
If you experiment with making pastry, you will
find that cold, firm fat makes the flakiest
pastry. The reason can be found in the oven.
Flaky pastry is made of many fine layers. In
the oven, it is fat that separates the layers of
dough. As the water in the dough turns to
steam and expands, it pushes these layers of
dough apart, forming the characteristic
blisters or flakes of good flaky pastry. The
greater the number of layers, the flakier the
final pastry will be.
( e) Speculate as to why cold fat would create
more layers in the dough than warm fat.
.... It's the Humidity
The dough mixture is sensitive. Even the
weather has an effect!
Water holds the flour and fat together.
When making pastry it is important to add only
enough water until lumps of dough start to stick
together. Any more water will develop extra
gluten, which toughens the pastry. However,if
bakers add precisely the amount of water their
recipes call for, they'll find that on humid days
their pastry will be tougher. Water vapour from
the air becomes part of the mixture.
(f) On rainy and humid days, you should add
less water than the recipe calls for. On dry
days, you should add more. Speculate on
what might happen to pastry dough that
doesn't include enough water.
(b) What factors determine how
Hands Off
Too much stirring or handling of the dough
toughens the pastry and also makes it less
flaky. Chefs recommend you use a fork or
pastry blender to mix the dough lightly, then
push it into a ball with your hands.
(g) Speculate on why handling the dough too
much is bad for the pastry.
Chill
Freshly mixed dough should be placed in a
refrigerator for 20 min before rolling.
Chilling allows the exposed flour particles to
evenly absorb moisture, making the dough
more uniform and easier to roll.
(h) If dough were set aside at room
temperature the flour would still absorb
water, but what else might happen in the
dough?
ltNntil
Other Pastry Ingredients
Ingredient
Function
sugars
Provides sweetness or aids yeast in producing
the gas for raising dough. Sugar can tenderize
dough and may help a baked product to brown.
salt
Brings out the flavours of other ingredients.
Reducing or omitting salt can cause dough to rise
too quickly, affecting shape and flavour.
baking soda,
baking powder
Baking soda. combined with an acidic
ingredient such as vinegar. lemon juice. or
molasses. produces gas to raise dough.
Baking powder is premixed. It contains baking
soda and the right amount of acid to react with it.
eggs
Egg yolks provide uniform flavour and texture
to cakes. Egg whites add air. When they are
beaten, they form a froth that includes lots of air.
SKILLS HANDBOOK:
Designing an Inquiry Investigation
much gluten is formed when
mixing pastry ingredients?
3. Should you store shortening in a
cupboard or in the refrigerator?
Explain.
1!:
Exploring
i
I
4. Does noise affect rising dough or
a baking cake? Could sound
waves cause rising dough to
collapse? Design an investigation
to test the effect of sound on
rising dough. Your procedure
should include safety precautions.
With your teacher's permission,
carry out your investigation.
!
Other Ingredients
Recipes often call for other ingredients than
the main three. Some of these are listed in
Table 1.
Troubleshooting
. An applesauce cake turned out flat, instead of
airy. The recipe called for baking soda, brown
sugar, and apple sauce. Both sugar and apple
sauce add acid to the mix.
(i) Did the baker make an error? What could
have gone wrong?
A couple from Edmonton who moved to
Toronto are disappointed with their pastry,
which is tougher now, at least in the summer.
(j) What would you recommend?
Pure Substances and Mixtures
29
-.,
SKILLS MENU
o Questioning
• Hypothesizing
ePlanning
~
• Conducting
o Recording
-
.• -~."••.III
-·,-~,:_ ..•. -··
-
-=-
•••
,'.
t,
-
•-.-"~L-.-
J_
:. .
11·
..,.,
• __
•.;
..,.~,;
WM iii
"But I put the same amount
of sugar in each one!"
Understanding factors that affect how quickly a substance dissolvesis
important to the manufacturing of medicines, dyes, and processed foods.
For example, some kinds of cold relief remedies are powders that must
be mixed with hot water. Scientistswho work for drug companies do tests
to ensure the powder dissolvesquickly in hot water. Understanding how
substances dissolvein other substances is an important part of their job.
When you add sugar to a drink, several factors affect how quickly the
sugar dissolves.Based on your experience, you probably have some idea
of what these are. But have you ever tested your ideas?
Question
What factors affect how quickly a solute dissolves in a solvent?
Materials
• apron
• safety _goggles
• beakers or clear plastic
cups
• marker pen
• hot and cold water
• thermometers
• powdered sugar
• sugar cubes
Part 1: Temperature
@)
IJ Using sugar cubes and
powdered sugar, plan a
controlled procedure to
test whether particle size
has an effect on the rate
of.dissolving.
IJ Plan a controlled
procedure to test whether
stirring has an effect on
the rate of dissolving.
1. Most brands of soda pop are
solutions that contain water,
dissolved sugar, and dissolved
carbon dioxide gas. When you
remove the cap from a cold
bottle of soda pop, you will
hear a faint whoosh as the
gas escapes. But when the
cap is removed from a warm
bottle, the whoosh is much
louder (Figure 2). What effect
does changing temperature
and pressure have on the rate
that carbon dioxide gas comes
out of a soda pop bottle?
Parts 2 and 3: Other Factors
-
Carry out the procedures you have
designed to test other factors.
Analysis
m Analyze your results by answering these
fJ Read steps 6 and 7. You
will design and carry out
tests for another two
variables (particle size,
stirring).
Making Connections
2. Suggest at least two
procedures that you
hypothesize would have no
effect on the rate of
dissolving. Explain why you
think they would have no
effect.
D Write a hypothesis for each variable you test in this investigation.
This is a con trolled
experiment investigating the
factors that affect the rate of
dissolving. A test for one of
the variables (temperature)' is
described in steps 6 and 7
below.
T-
Reflecting
Hypothesis
Procedure
.TT'
Analyzing
• Communicatmg
The Rate of Dissolving
Experimental Design
•. _
Dt\Mi#J
Soft drinks are solutions that contain
dissolved gases among other substances.
questions.
E) Mark two containers as
follows: C (cold), H (hot).
• Pour cold tap water in the
container marked C until
it is three-quarters full.
• Pour the same amount of
hot tap water into the
container marked H.
II Add 5· mL of sugar to
each cup.
(a) In which cup does the
solute dissolve faster?
(a) List three factors that affect how quickly a
solute dissolves in a solvent.
(b) What effect does each of these factors
have?
(c) When testing the effect of stirring on
dissolving, what was your independent
variable?
( d) Explain how you controlled other
variables.
~ (a) Record the
temperature of the
water in each cup.
( e) Use the particle theory to explain how
each of the factors affects dissolving.
Include a sketch in your answer.
El Write down the steps for
your procedures and
submit them to your
teacher for approval.
30
Unit 1
SKILLS HANDBOOK:
@ Predicting and Hypothesizi~
@ Designing an Inquiry Investigation @) Identifying Variables and Controls
Pure Substances and Mixtures
31
r. , .a
Supersaturation
With very few solid solutes, it is possible to create a solution
that is more than saturated. A solution that contains more of
the solute than. would be found in a saturated solution is
called supersaturated.
A supersaturated solution can be made with certain
solutes by starting with a hot saturated solution at high
temperature, and then allowing the solution to cool slowly.
If the solution is not disturbed, all the solute may remain
dissolved.Normally, as a solution cools the solute particles
lose energy. This allows the attraction between a few of the
solute particles to draw them together into the crystal
pattern of the solid. A crystalline solid forms in the solution.
In a supersaturated solution, the solute particles are not able
to get into the crystal pattern.
If the container holding· a supersaturated solution is
struck lightly with a solid object (a spoon or a stirring rod,
for example), the resulting vibrations may cause some of the
solute particles to move into the crystal pattern.
Immediately, the rest of the extra solute willjoin the crystal
and fall out of solution. You can produce a similar effect by
adding a seed crystal of the solute for the excess solute
particles to build on (Figure 2).
Saturated or Unsaturated?
Have you ever made a drink by dissolvingflavour crystals in water and found that
it tasted "watery"because you didn't add enough crystals? This happens when you
don't have the right concentration of solute in the solvent. Concentration is the
amount of solute dissolved in a given quantity of solvent or solution.
Solutions with a low concentration of solute are called dilute solutions. To
make the flavour of your drink stronger, you must increase the concentration of
the solute by adding more flavour crystals to the same amount of water. Solutions
with a high amount of solute are referred to as concentrated solutions.
Since both dilute and concentrated solutions still contain unfilled spaces
between the solvent particles (Figure 1), they are both unsaturated solutions.
The maximum amount of solute in a solution is the amount that fills all the
available spaces between the solvent particles. A solution in which all the spaces
are filled is a saturated solution. If you try to strengthen the flavour of your drink
by adding still more flavour crystals to a saturated solution, the crystals will simply
sink to the bottom of the glass without dissolving.
Exactly How Much Solute Can You Add?
The solubility of a solute is the exact amount
of solute required to form a saturated solution
in a particular solvent at a certain
temperature.
The solubility is different for each
combination of solute and solvent. The
amount of solute needed to saturate a certain
volume of solvent varies enormously. A
solution of one substance in water, for
example, may be saturated when only a little
of it has been dissolved. On the other hand, a
saturated solution of another substance in
water may contain a lot of solute. In Table 1
you can see that, at any temperature, the
amount of sugar that will dissolve in 100 mL
of water is greater than the amount of table
salt, which in turn, is greater than the amount
of baking soda.
litihtll
Temperature
baking soda
0°C
6.9 g/100 ml
20°C
9.6 g/100 ml
50°C
14.5 g/100 ml
table salt
35.7 g/100 ml
36.0 g/100 ml
36.7 g/100 ml
sugar
179 g/100 ml
204 g/100 ml
260 g/100 ml
32
Unit 1
1. Describe how you can tell
the difference between a
saturated solution and an
unsaturated solution.
2. Is the solubility of all solutes
the same?
Making Connections
3. Use the particle theory to
explain why some substances
do not dissolve in a particular
solvent, while others do.
4. Rock candy is made by
dissolving sugar in warm
water to form a saturated
solution, then allowing it to
cool. Based on what you
know about solutions, explain
how the candy forms.
Dilute, concentrated, and saturated solutions
C, In a dilute solution,
the solute particles
fill only some of the
available spaces
between the solvent
particles.
,e,d~
WMiiJ
C, Supersaturated
0
In a concentrated
solution, the solute
particles fill most of
the available spaces
between the solvent
particles.
In a saturated
solution, the solute
particles fill all of the
available spaces
between the solvent
particles.
D)sign Challenge
What would you have to
take into consideration
designing your water
purification system for
Challenge 1?
solutions are rare
because they are very unstable.
They contain more dissolved solute
than would normally occur at that
temperature. Adding a seed crystal
changes the nature of the solution.
solute particle
solvent particle
G
Some Solubilities in Water
Solute
L@jijjj•
Understanding Concepts
0
•
The seed crystal begins to grow
as excess solute particles are
attracted to and become part of
the pattern of particles in the
seed crystal.
G All excess solute
saturated
solution
•
has now
solidified around the seed crystal.
The solution is now saturated at
that temperature.
-
Comparing Solubility
•
Pour 100 mL of water into each of two
400-mL beakers.
•
Add 50 g of salt to one beaker and 50 g
of sugar to the other.
•
Stir both at the same rate.
1. Does the same amount of both solutes
dissolve in the water?
2. What does this tell you about the
solubility of salt and sugar in water?
Pure Substances and Mixtures
33
SKILLS MENU
O Questioning
Hypothesizing
OPlanning
• Conducting
• Recording
• Analyzing
• Communicating
Understanding Concepts
Solubility and Saturation
1. If a solution is saturated at
20°C, will it also be saturated
at 40°C? Explain your answer.
You have already learned that the solubility of solutes in solvents is
affected by temperature. But how much does solubility go up or down
as the temperature rises?
Question
Are changes in the solubility of drink crystals in water predictable?
Hypothesis
D Write a hypothesis for this investigation.
Experimental Design
The solubility of drink crystals in water will be measured at different
temperatures. You will be able to graph how solubility changes
according to temperature.
Making Connections
Materials
•
•
•
•
•
•
•
•
•
•
•
apron
safety gqggles
drink crystals
clear container
100-ml beaker
250-ml beaker
100-ml graduated
cylinder
water
balance
stirring rod
thermometer
2. Suppose you mix lemon juice,
sugar, and cold water to make
lemonade. After stirring, there
is still some undissolved sugar
at the bottom of the glass.
(al Why didn't all the sugar
dissolve?
(bl Which type of sugar
solution was formed?
(cl What type of sugar solution
would form if you heated
the lemonade?
Exploring
The solubility of all solutes changes according to temperature.
3. Predict what will happen to a
hot, saturated solution of drink
crystals in water as it cools.
Explainyour prediction. With
your teacher's permission, try
it. Was your prediction correct?
Procedure
Analysis
IllAnalyzeyour results by
answering these questions.
fJI Measure the mass of a
100-mLbeaker.
~ (a) Record the mass of the
beaker.
• Half-fill the beaker with
drink crystals.
• Measure the total mass of
the beaker and the
crystals.
~ (b) Record the mass of the
beaker and crystals.
( c) Calculate the mass of
the crystals.
II Fill a graduated cylinder
with 100 mL of tap water.
• Pour the water in to a
clean 250-mL beaker.
D Slowlyadd crystals from
the beaker to the water,
stirring constantly, until
no more crystals dissolve,
and you see crystals
starting to collect on the
bottom.
• Measure the water
temperature with a
thermometer.
~ (a) Record the
temperature of the
water.
El Measure the mass of the
beaker and unused
crystals and record it.
(a) Calculate the mass of
the crystals you added
to the water.
~ (b) Record the solubility
of the drink crystals in
water at the measured
temperature, in
g/100 mL.
m Repeat steps 2 to 5 using
water at 3 other
temperatures, using a
mixture of hot and cold
tap water.
~ (a) Record the solubility
of the crystals at each
temperature.
(a) How did you know when
you had created a
saturated solution?
(b) From your data and the
data of other groups in
your class, draw a graph of
solubility versus
temperature for drink
crystals in water.
(c) Based on your graph,
what happens to the
solubility of drink crystals
in water as the
temperature of the water
increases?
(d) Using your graph, predict
the solubility of drink
crystals in water at 80°C.
34
Unit 1
SKILLS HANDBOOK:
@ Predicting and Hypothesizing @ Constructing Graphs
Pure Substances and Mixtures
35
r
1.10 Inquiry Investigation
SKILLS MENU
O Questioning
O Hypothesizing
ePlanning
• Conducting
• Recording
• Analyzing
• Communicating
Making Connections
Separating Mixtures.
You have learned that a mixture consists of two or more pure substances.
Because each of these substances has different properties, they can be
separated from each other, as shown in Figure 1. One of these properties
may include the ability to form a solution in a particular solvent.
Materials
Procedure
• safety goggles
l!J Once your procedure is approved, carry it
• apron
• table salt
• pepper
Question
What methods can be used to separate a heterogeneous mixture
consisting of three substances?
• sand
Experimental Design
By analyzing a mechanical mixture and studying the separation
·techniques illustrated in Figure 1, you will come up with a procedure for
separating the substances.
II Using what you have
El Examine a small amount
of each of the three
substances in the mixture.
IJ Using whatever equipment
~ is available and your senses
of sight and touch, observe
and record in a table the
physical properties of each
substance.
36
Unit 1
2EJ
observed about the ·
properties of the
substances in the mixture
and the information in
Figure 1, develop a
detailed procedure for
separating the substances.
At the end of your
procedure, you must have
three dry solids, each in a
plastic bag. Your
procedure must include
labelled diagrams to
illustrate how equipment
will be used.
(b) water, flour, and marbles
(c) vegetable soup, salt, and water
(a) Record the appearance of your
substances and mixture after each step
is complete.
(d) water, iron filings, and soil
2. (a) Is there any commercial
WM iii
• mechanical mixture (salt,
sand, and sawdust)
Some separation techniques
separate particles suspended in a
liquid?
• magnet
• 3 plastic bags
• other materials and
equipment as needed
allowing parts to float or settle
3. Draw a flowchart to show how you
would separate a mixture of iron
filings, sand, salt, stones, and
sawdust.
filtration
(using a variety of filters)
Analysis
II Analyze your results by answering
these questions.
attracting one of the
substances to a magnet
picking apart the bits and pieces
(a) Which physical property did you
use to separate the first substance
from the mixture?
(b) Which physical property did you
use to separate the remaining
two substances in the mixture?
El Submit the procedure to
your teacher for approval.
advantage to using settling
instead of filtering to remove
particles from a liquid? Explain.
(b) Why isn't settling always used to
• iron fillings
If you use a hot plate to
heat a solution, the
liquid may start to "spit"
toward the end of the
heating. Be prepared to
remove the dish from the
hot plate with tongs if
this occurs.
safety goggles.
(a) water, sugar, and sand
out.
• sawdust
Hypothesis
Examining the properties of the substances in a mixture will enable you
to choose a technique that allowsyou to separate each substance from
the mixture.
D Put on your apron and
1. Explain which separation techniques
you might use to separate the
substances in each of the mixtures
below:
( c) Do you think you recovered all of
each substance in the mixture?
How might you improve your
procedure to ensure that as
much as possible of each
substance is recovered?
dissolving one substance
but not the other
evaporating one part
O)sign Challenge
Your Challenge requires that
you separate substances in
a mechanical mixture. Which
of the techniques you have
learned here will help you
solve the Challenge?
SKILLS HANDBOOK:
@ Designing an Inquiry Investigation
@Writing
a Report
(d) Submit a report on the
@ investigation that includes your
observations, the procedure you
used, and a description of how
you would improve your
procedure if you had to do the
separation again.
Pure Substances and Mixtures
37
I
1.11
Wii'iiil
Using Solutions of Gases
Exploring
A good, warm fire needs dry
wood that will burn easily
and oxgyen from the air.
1. Scuba divers who work at
considerable depths underwater
are careful not to surface too
quickly to avoid a condition called
the "bends" or decompression
sickness.
Because we can't see gases or feel them unless they move, we often
forget that they exist! But we actually use many different gases in
everyday life.
(a) Use a variety of print and
Air
Neon for Light
You learned earlier that air is a solution of
gases that includes nitrogen, oxygen, argon,
and carbon dioxide. There are also varying
amounts of water vapour and tiny amounts of
several other gases. All of these gases are pure
substances.
We breathe air every moment. Our lungs
separate oxygen from the solution, and add
carbon dioxide and water vapour. As a result,
the solution of gases we breathe in is different
from the solution we breathe out.
We also use air that has been compressed
under high pressure for transportation and
recreation (Figure 1) .
Neon is a gas that has transformed our city
streets. Brightly coloured neon lights are
made of glass tubes that contain neon or
other gases that glow when an electric current
is passed through them (Figure 2). Neon
glows an orange colour, but by changing the
colour of the glass, it is possible to make
neon-filled tubes that glow red, green, or even
blue. Neon and the other gases are pure
substances, but neon tubes usually contain a
gas solution rather than pure neon.
DtMiil
E)
fl)
Compressed air is used
to fill bicycle and car tires
for a smooth ride.
Gases for Surgery
Gases are an important part of surgical
operations (Figure 3). During an operation,
the patient must stay unconscious, yet still
breathe. This is arranged by giving the patient
a gas solution that includes oxygen and
another gas, such as nitrous oxide, that causes
the patient to stay unconscious. The person
responsible for controlling the flow of these
gases during the operation is a specialized
doctor called an anesthesiologist.
Compressed air is
also used to fill air
mattresses for
floating on water.
DiMiil
G
38
Unit 1
Divers carry compressed
air in a tank on their
backs so they can
breathe air for long
periods underwater.
During surgery, the
anesthesiologist controls the
amounts of each gas in the
solution the patient breathes.
The patient must stay
unconscious but also breathe
normally during the
operation.
electronic sources to research
this condition.
(b) Prepare an information
pamphlet to inform scuba
divers about this condition.
2. Methane gas has other surprising
locations and uses. Use a variety
of print and electronic sources to
find out more about methane in
the ocean, as an alternative fuel,
and its effect on the atmosphere.
Present your results as a poster
that informs others about the
importance of methane in our
lives.
Gases for Burning
It is the oxygen in the air that allowsfuels to
burn. When we burn wood in fireplaces or
gasoline in cars, the carbon in these fuels
reacts chemically with oxygen in the air,
forming carbon dioxide and water and giving
off a lot of heat. This heat is used to provide
warmth, cook food, or to supply energy for
moving vehicles (Figure 4).
Sometimes the fuel itself is also a gas. For
example, natural gas is piped into many
homes to provide heat when it is burned in a
furnace, a water heater, or a stove (Figure 5).
Natural gas is actually a solution of several
similar gases, with methane as the solvent.
Like wood, oil, and coal, methane contains
carbon. Natural gas is found deep
underground in pockets, usually near
underground oil deposits. It is believed that
oil and natural gas both formed from
organisms that lived millions of years ago and
were buried under many layers of rock and
soil. Once a gas well is drilled down through
the rock to a gas pocket, the gas flows up to
the surface on its own. From the surface,
thousands of kilometres of pipelines bring the
gas into our homes. Figure 6 shows a pipeline.
or air.
Wi'iiiil
Extensive networks of
gas pipelines extend
from gas wells in
western Canada to the
large cities of central
Canada.
Pure Substances and Mixtures
39
i
I
~
1.12
Glass: One of the Ceramics
Glass is another type of solution-actually a
Products from Raw Materials
In the beginning of this unit you learned that pure substances can be
mixed together to form solutions that are liquid, gas, or solid. What are
solid solutions and are they an important part of our lives (Figure I)?
Mostmetals we use are combinations of two or more metals mixed
together in a solid solution called an alloy. An alloy is a homogeneous
mixture of a metal with other substances. Alloys allow scientists and
engineers to design metals that have specific properties depending on
what they are used for. Steel is formed in a process that takes iron from
iron ore and carbon from coal. Usually small amounts of other metals
are mixed in to give the steel different qualities. Chromium and nickel,
for instance, are often added to make the steel resistant to rust, giving it
the name stainless steel. Adding zinc to copper makes brass, an alloy that
is stronger than copper alone and is resistant to corrosion. It is used for
ornamental objects on the exterior of houses, such as house numbers
and mailboxes.
The idea of making alloysis actually thousands of years
old. Early civilizationsdiscovered that if you pour a small
amount of melted tin into melted copper, the tin will
dissolvein the copper to form a new substance, bronze,
that is much harder than either metal. Bronze was made
into furniture, jewellery, tools, armour, and weapons.
supercooled liquid. The main raw material'
used to make glass is quartz.
Glass is a ceramic product we use daily. In
the process of making glass, small amounts of
limestone and potash are mixed with the silica
at high temperatures, and then allowed to
cool. While it is still liquid, glass can be poured
onto a flat surface to form a sheet, from which
we can make windows.Hot glass can also be
moulded into shapes, such as
vases, glasses, and bottles.
Glass Fibres
lii'hii
Many musical instruments, such as the saxophone, trumpet, and
tuba, are made of copper and zinc mixed together to form brass.
\
Modern Alloys
We still find uses for bronze, such as in statues. However,
in the past few decades metallurgists (who study metals)
have experimented and come up with thousands of
different alloys, each having its own special properties.
Some alloys are designed to resist heat, as in Figure 2,
others to be strong, or light, or flexible.
· One important modern addition to the list of useful
metals is aluminum. Aluminum is very light and is used
extensively in alloys used to make automotive engines,
airplanes, and bicycle frames. Aluminum helps reduce
weight.
Magnesium is a metal that is even lighter than
aluminum, but it is more expensive. When light weight is
crucial, as in the bicycle in Figure 3, magnesium alloys
maybe used.
WM#J
Rockets and jet engines are made from alloys
that include tungsten, which has the highest
melting point of all metals (3410°C).
Purified metals, such as aluminum, nickel,
or copper, and alloys, glass, ceramics, and
plastic are all processed or manufactured
from raw materials. Many of the products
we buy have been shaped from those raw
materials. In every case, the raw materials
used for each item have been chosen
because of their special properties.
•
Ceramics, including pottery, bricks, cement, and glass, are
40
Unit 1
Some new types of ceramics, with different
combinations of ingredients mixed in with
melted silica, are able to withstand extremely
high temperatures. These materials are used
in the heat shields of spacecraft so that they
can withstand the fiery temperatures
encountered when re-entering Earth's
atmosphere.
Materials with a Purpose
Ceramics
made mostly from silica, and are another type of mixture.
The mineral quartz is the crystalline form of silica and the
source of raw materials for ceramic products. Silica
particles are also often found in beach sand.
Other Types of Ceramics
Glass can also be drawn out
into fibres so thin that they
are flexible but still allow
light to pass through them, as
shown in Figure 4. Thin glass
fibres have revolutionized our
worldwide communications
systems.These optical fibres
can carry thousands more
signals than electrical cable
made of copper wires.
Optical fibres have provided
the technology for the huge
increase in electronic
communication that has
occurred in recent years.
liiii'iiil
Bicycle frames used by racers are very light because
of the magnesium dissolved in the other metals.
Look around the classroom and make
a list of the objects that you see.
2. Indicate if the materials are natural,
such as wood, or if they have been
processed, such as plastic.
3. Record some of the properties of the
object and explain why the particular
materials were chosen for each object.
4. Are the materials used alwaysthe best
choice in each case? List any alternative
materials and explain why they would
be better.
1. Beside each object in your list, write the
materials you think it is made from.
Pure Substances and Mixtures
41
Understanding Concepts
Glass for Insulation
Hot, molten glass can also be spun into small
glass fibres, which are sprayed with a type of
glue to form thick mats. These light, fluffy
mats are used as insulation in houses and
other buildings to keep in their heat. As an
energy-conserving measure, as shown in
Figure 5, the use of insulation in buildings has
become an important feature.
LUMl4i
ceramics?
Oil is the main raw material for
making plastic products.
liquid petroleum
~
I
gases~
~
kerosene
Plastics
Plastic is a modern material that we use in a
huge number of products, from ice skates and
toys to lawn chairs and tables (Figure 6).
Plastic does not occur naturally. It is
manufactured in a process that takes several
steps, beginning with oil and gas.
COOLING
Oil and Gas-the Source of
Plastic
We use plastic everywhere, for almost any activity.
(b) Which raw material is common to all
Making Connections
jetfuel
Wil'iiiii
2. (a) What are the main raw materials
used to make glass?
Utii'iiii
Glass-fibre insulation matting is
another important use of glass.
Crude oil pumped up from the Earth
(Figure 7) is a raw material that is processed
into many products, including plastic. Other
products made from crude oil include
gasoline, waxes, and asphalt for paving roads.
1. Explain in your own words what an alloy
is and describe its significance in the
manufacturing of metallic products.
Crude oil is a mixture of many different
pure substances that can be separated from
each other in a refinery, as shown in Figure 8.
The lighter substances in the crude oil are .
combined chemically with a pure substance
from natural gas to form the many different
types of synthetic materials that we call plastic.
Materials Have Different Uses
Designers, engineers, scientists, and artists
all work with materials, and must decide
which material best suits the purpose that
they have in mind. For example, when
designing a spacecraft, engineers may have
to select a different alloy or ceramic material
for each part. Some parts must be extremely
strong, while others must be resistant to
heat, to cold, or to bending.
A glass blower may choose to add lead to
glass to make a fine crystal. Glasswith lead
in it sparkles like a diamond when it is cut
into patterns. And, of course, plastic varies
widely,from the flexible form used to wrap
food to the harder form used in casings, for
example, around telephones and computers.
We are surrounded by different materials. As
consumers, we must not only make decisions
about which items and which materials best
suit our needs, but also about what will
happen to the materials when the product is
no longer useful.
crude oil
D.esign Challenge
(a) You have learned about some finished
products-plastics, glass, ceramics, metal
alloys. Are any of these the best choice of
material for the structures you must make for
your Challenge? What other materials could
you use?
3. If you had a choice of flying in a glider
made of steel, or one made of a steel
and manganese alloy, which would you
choose? Why?
4. Many human body parts can now be
replaced by artificial parts. What
properties would designers and
engineers need to consider when
choosing the materials or substances to
create an artificial limb?
Exploring
5. Soft packing beads, polar fleece jackets,
and the wheels of inline skates are each
made of a different type of plastic. Using
electronic and print sources, research the
differences between these plastics.
Make a chart of the different types of
plastics and what properties they have
that make them suitable for the use
specified.
Reflecting
6. There are many kinds of steel with many
different properties. These different
@ properties are the result of different
materials added to the steel. Using
electronic and print media, research how
steel is made. Choose one kind of steel
and create a poster illustrating how it is
made, what it is made of, and how it is
used.
7. "Modern products have better designs
and are made of better materials than
products in the past. Modern products
may also have fewer environmental
problems than products in the past". Do
you agree with these statements? Give
examples along with reasons for your
answers.
(b) Different substances are used to make the
various types of plastic. In the recycling
Challenge, is it important to know which
plastic objects can be recycled together? Are
there plastics you cannot accept?
42
Unit 1
SKILLS HANDBOOK:
@ Research Skills
Pure Substances and Mixtures
43
SKILLS MENU
o Identify a Problem
• Planning
eBuilding
eTesting
eRecording
eEvaluating
eCommunicating
Evaluate
Concrete for Construction
1. Did you record any difference
in the mass required to break
the two beams?
Materials
Designers and engineers must make decisions about using the best
materials for a given purpose. Concrete is a material used in a variety of
construction applications-buildings, dams, and sidewalks.It consists of
two materials: crushed gravel and cement (Figure 1). The cement,
when wet, is the "glue" that holds the crushed gravel together. Cement
is made from clay and limestone. The gravel adds strength to the
cement. But does a sidewalkneed to be as strong as a dam? Is concrete
as strong as cement?
Problem
How strong is cement alone compared to concrete? A construction
company is preparing to build a bridge out of concrete. In order to
safely ensure that the weight of people and equipment crossing the
bridge will be supported, it needs to choose the stronger material of
concrete or cement.
Design Brief
Youwill compare the strength of cement and concrete by building a
cement beam and a concrete beam and comparing them.
• apron
• safety gloves
• mask
• empty 1-L milk carton
• scissors
• masking tape
• plastic sheet
• concrete mix
• cement mix
• 2 containers for mixing
• mortar trowel
• water
• wire
• hook
• pail
• bathroom scales
Note that time is an
important element in this
investigation.
Build
2. What differences did you
notice between the dry
cement mix and the dry
concrete mix? What
differences did you notice in
the beams? How do you
explain the difference in
strength of the two materials?
3. Which material would the
construction company choose
for its purpose?
Making Connections
A
U
Concrete and cement mixes are corrosive. Do not
handle with bare hands. Wash hands with soap and
water after you complete this investigation.
Test
4. Concrete varies according to
how it will be used. What do
you think might be the
difference between the type
of concrete used for dams and
the type used for sidewalks?
5. The massive, 13 km
Confederation Bridge links
@ Prince Edward Island with
New Brunswick. What special
properties do you think would
be required for the concrete in
this bridge? (Hint Consider
year-round possibilities.)
Research on the Internet what
ingredients the engineers
added to the concrete for the
bridge and their purpose.
Exploring
D Seal the top of a milk
carton with masking tape
and lay the carton on its
side.
• With scissors,cut away
one side of the carton.
• With masking tape, tape
the cutawaypiece into the
middle of the carton to
form a barrier.
fJ In a container, add water
to 2 kg of concrete mix,
stirring the concrete and
water together until all
the dry powder is wet.
• Use the trowel to fill one
side of the milk carton
with the concrete mix.
IJ Repeat step 2 using
cement mix instead of
concrete mix, and pour
this mix into the other
half of the carton.
• Allow the cement and
concrete to harden for
two weeks, then peel away
the carton.
II Place the cement beam
over a gap between two
tables.
• Loop a piece of wire
around the middle of the
beam and attach a hook.
• Suspend the pail from the
hook.
El Gradually add sand or
water to the pail until the
beam breaks.
• Measure the mass of the
pail and its contents.
~ (a) Record the mass
needed to break the
cement beam.
E) Repeat steps 4 and 5 with
the concrete beam.
6. Try making your own concrete
mix by combining a different
@ amount of gravel with the
cement. Predict what will
happen if you construct a
beam with each different
mixture and test its strength.
With your teacher's
permission, try it.
D)sign Challenge
Would concrete be a good
choice of material for any part
of your Challenge?
44
Unit 1
SKILLS HANDBOOK:
Research Skills (3F) Testing and Evaluating a Prototype
Pure Substances and Mixtures
45
1
1.14 Inquiry Investigation
SKILLS MENU
O Questioning
• Hypothesizing
ePlanning
1_
• Conducting
• Recording
Question
Will each of three common solvents (water, mineral spirits, and
ethanol) be able to remove all of the different stains (lipstick, ballpoint
ink, and felt-tip ink) from fabric?
Hypothesis
@ DWrite a hypothesis for this experiment.
Experimental Design
II Design a controlled experiment to test your hypothesis.
@
• Your experimental design must include a method for placing the
stained fabrics in the solvents and removing them without having
your hands touch the solvents.
• Your experimental design must include a description of the variable
you are testing and how you are controlling other variables.
• Your experimental design must include a description of how to
dispose of the solvents safely.
IJ Explain in detail how you will investigate the ability of each solvent
·~-
•
~
- b
-
..::_· -
'
Materials
safety goggles
apron
gloves
labelling materials
water
ethanol
mineral spirits
graduated cylinder
lipstick
ballpoint pen
felt-tip pen
pieces of cloth
other materials and
equipment as required
e
Making Connections
Turpentine is an
effective solvent for
cleaning (dissolving)
oil-based paints from
brushes. Water is
effective for cleaning
(dissolving) latex
paints, which are
made with water
1. Make a list of cleaning
solvents that you can find in
your home. Carefully read the
labels on each. Separate them
into two groups: those that
can be used without special
precautions, and those that
require special handling. What
conclusion can you make
about the safety of
commercial solvents?
2. Imagine that you run a drycleaning business. You have a
choice of five solvents to use.
Table 1 gives some important
properties of each of them.
Which solvent would you use?
Explain your reasons.
Reflecting
3. Look at the properties of the
given solvents in Table 1.
What environmental concerns
exist if they are disposed of by
pouring them directly into the
sewage system? Suggest
some alternative methods
of disposal.
Do not touch the
solvents with your
hands.
• Ethanol and mineral
spirits can cause
damage to the skin
and eyes.
• Mineral spirits are
poisonous if
swallowed.
• Ethanol is
flammable.
Analysis
IJI Analyzeyour results by
answering these questions.
(a) Did any single solvent
dissolve all three of the
stains?
to remove each stain.
(b) If your answer to question
(a) is no, which solvent
removed the most stains?
IJ Create a table for recording your data.
II
Submit your design, your procedure,
and your table to your teacher for
approval.
IGifitil
Solvent
Properties
turpentine
methanol
isopropanol
ethylene
chloride
excellent
very good
very good
excellent
excellent
dichloromethane
Procedure
dissolves grease?
Isl Carry out your experiment in a well-
flammable?
no
yes
yes
yes
yes
toxic vapour?
yes
no
yes
no
yes
ventilated room.
WM iii
Detergents are excellent solvents for
dissolving most common stains on clothes.
46
Unit 1
'
-
• Communicating
UPi'iiil
•
•
•
•
•
•
•
•
•
•
•
•
•
.
e Analyzing
Solvents in the Laundry
Most commercial cleaning agents are simply solvents. As you learned
earlier, a substance may dissolve in one solvent but not in another.
Stains are examples of substances that behave in this way.Water can
dissolve some stains in clothes, but detergents are often added to
dissolve many types of stains more effectively (Figure 1). The resulting
mechanical mixture is then rinsed away.
Commercial dry cleaners also remove stains from clothes, but they
use specific solvents, such as dichloromethane, that won't damage
certain fabrics. From paint removers (Figure 2) to metal surface
cleaners, industries are alwayson the search for better cleaning solvents.
-
SKILLS HANDBOOK: @Predicting and Hypothesizing
@ Designing an Inquiry Investigation
(c) A good cleaning solvent
must be nontoxic (not
poisonous), should not be
flammable, and must
dissolve the stains it is
being used on. Does your
most effective solvent
meet these criteria?
Explain.
Pure Substances and Mixtures
47
r
'
1.15
The Importance of Water
Did you know that water covers about 80% of
Earth's surface? So why all the fuss about
conserving water? The reason is that the
oceans contain salt water that is undrinkable,
and most of the rest is locked in polar ice and
glaciers. That leaves less than 1 % that is
drinkable. But Canada, with less than 1 % of
the world's population, has 22% of the world's
fresh water. And Ontario has 228 000 inland
lakes, plus a large share of the Great Lakes.
We must have more than enough.
Not quite! Water is
used in more ways than
you might think.
Everydayyou use
solutions that have water
as their solvent. The tap
water you drink, for
instance, contains
dissolved minerals that are
absorbed by your body to
97 .2o/o salt
help carry out your life
functions and to
strengthen your bones.
You use water solutions to
wash your clothes and
your body. Water is also
the solvent for solutions
used in different industrial
processes.
The problem is that
people need clean water-water that has been
filtered, processed, and
purified; water they can
safely drink. Tests show
that our lakes and rivers
contain more substances
than ever that make the
water less desirable for
drinking. How do these
substances find their way
into our water supply?
48
Unit 1
Understanding Concepts
D)sign Challenge
Our lakes, once a source of clean water,
now contain hundreds of dissolved substances.
Some of the substances come from soil, rocks,
and air, some from animals and plan ts, and
some from the activities of people.
Manufacturing, refining, sewage, waste
disposal, farming, incinerating-these all
produce substances that end up dissolved or
mixed into the water that we depend on to
live (Figure 1) .
1. With all the fresh water in Canada,
why would Canadiansworry about
the supply of drinking water?
A recent heavy rainfall overloaded a sewage
treatment facility, causing sewage to flow into the
river from which drinking water is taken. Nature
can deal with such flows, if they are small. Bacteria
will break down some solids, and particles of other
solids will gradually fall to the bottom of the river.
What can you learn from "nature's way" that will
help you solve your Challenge of purifying water?
2. Describe two ways in which water
can be polluted from distant
sources. Draw a concept map to
illustrate your findings.
Making Connections
UPMll•
The fresh water in our lakes contains hundreds of dissolved and mixed
substances. Some come from the soil, rocks, and air, some from animals
and plants, and some from the activities of people. Manufacturing,
refining, sewage, waste disposal, farming, incinerating- they all produce
substances that either dissolve or settle in water.
dioxins
absorbed from polluted air
over the lake
II
water
petroleum products
from ships and from
---
3. (a) How is water being used by
people or animals in the
picture on these pages? Make
a list of the uses. Add any
other uses of water that you
can think of.
(b) Put a star (*) beside each use
of water that you think
involves the addrtion of
substances to the water. If
you know the names of the
substances, write them down
beside the use.
4. Suggest some strategies for
conserving water in the following
places:
(a) bathroom
(bl kitchen
(c) outdoors
Exploring
5. Water is easy to waste. Place a
soil nutrients
washed into the lake through
normal erosion and poor farming
plastic measuring cup under a
slowly dripping tap, either at
school or in your home. Measure
the time it takes to fill the cup.
How much water is lost in one
hour by a leaky tap? in one day? in
one month?
Reflecting
chemicals used on lawns,
gardens. and crops to fight
insects or to promote growth are
washed into the lake
calcium and magnesium
minerals absorbed from
limestone m the bed of the lake
and its feeder streams
6. Often liquid wastes are disposed
of by pouring them down the
drain. What problems can be
caused by this practice? What
problems are caused by industries
and municipalities that dump
pollutants directly into lakes and
rivers?
Pure Substances and Mixtures
49
1.16
Turbidity
Testing Water Quality
Clean drinking water is essential for human
survival.It must be clear and free of dangerous
living things and chemical poisons. For aquatic
animals such as fish, water must include
enough dissolved oxygen for breathing. Mostly,
though, clean water is defined by what it
doesn't contain. There are tests we can do to
show what is in the water we drink or swim in.
Dissolved Oxygen
The amount of oxygen dissolved in water is
one of the most important indicators of water
quality, since oxygen is necessary for aquatic
organisms to live.
Oxygen in air is able to pass from the air
-and dissolve into surface water. Oxygen is also
produced in the water by aquatic plants. In the
process of converting the energy of the sun,
water, and carbon dioxide into food, plants
release oxygen as waste. At night, though,
aquatic plants consume dissolved oxygen and
release carbon dioxide. But oxygen is also
consumed by animals and bacteria in the
water, as you can see in Figure 1.
Most aquatic organisms require a dissolved
oxygen concentration of 5 to 6 parts per
million (ppm) for normal growth and activity.
Levels below 3 ppm are stressful for most
aquatic organisms, and levels below 2 ppm are
too low for fish populations to survive.
Acidity
Most water in nature contains dissolved
substances that make it slightly acidic or, the
opposite, slightly alkaline. Strong acids and
strong bases are dangerous to living things, as
both are corrosive. Figure 2 shows the
pH scale, which is used to classifyhow acidic
or alkaline a solution is.
A healthy lake typically has a pH of about
8, which is slightly alkaline. Lakes that receive
a lot of acid from rain or snow may end up
with a pH of 4 or 5, which is acidic. In water
that is acidic it is difficult for certain species
of fish to survive. However, many lakes are
surrounded by rocks that naturally neutralize
the acid, as you can see in Figure 3.
You can test how acidic or alkaline a water
sample is with specially coated "pH paper"
that changes colour. Each colour corresponds
to a pH number.
WM iii
The pH scale ranges from O {strongly acidic) to 14
(strongly alkaline). Solutions at both ends of the scale
are highly corrosive. The middle of the scale, a pH of
7, is neither acidic nor alkaline, so it is described as
neutral. Pure water is neutral-it has a pH of 7.
Hardness
Water that contains small amounts of dissolved minerals
is called soft water. Rain water is the best example of
natural soft water.
Most water in nature contains a variety of dissolved
substances. Water that contains relatively high amounts of
dissolved calcium, magnesium, or sulfur is called hard
water. Hard. water is difficult to clean with, as soap does
not form a lather in it. Hard water containing dissolved
sulfur may have an unpleasant taste.
The dissolved substances come from the soil and rock
that water passes over or through. For example, rain
water that ends up in a stream that flows over limestone
will dissolve calcium from the rock.
D)sign Challenge
In the water purification Challenge,.you must propose some
tests to measure the safety of the water. Which of the
tests of water quality mentioned here should you include?
Would you need others?
1. Make a chart that lists four
important measures of the quality
of water. Note how each is
important to our survival and
quality of life.
2. (a) Describe the cycle of oxygen
in a lake.
(b) Predict what can occur if any
part of the cycle is disrupted.
Making Connections
3. Imagine that people start pumping
sewage into the stream that flows
into the lake in Figure 1. Sewage
water contains many small
suspended solid particles. Explain
what effects you would expect to
see on:
(a) the turbidity of the lake
(b) the oxygen content of the
lake
(c) plant and animal life in the
lake
Exploring
4. Using electronic and print
sources, research how hardness
is eliminated from water. either
during the water purification
process or by consumers before
they use it. Prepare a chart listing
the different techniques.
ammonia
Oxygen enters the water from the atmosphere
Acid rain dissolves
in lake and stream
Fish and other aquatic animals
breathe m and use up oxygen
Understanding Concepts
small solid particles are often suspended (floating) in
water. These particles make the water cloudy. Turbidity is
a measure of how cloudy water is. If water contains large
amounts of suspended solids, the water will be so cloudy
that it blocks sunlight from reaching aquatic plants.
Without sunlight, ·the plants will die. Suspended solids
can be caused by soil erosion, wastes from animals and
plants, human waste, and waste from industry.
Special meters, using light and a light detector, can be
used to measure turbidity.
Water flowing through or
over limestone dissolves
minerals and
becomes alkaline
•'
·-.llft normal rain
Bacteria use up oxygen as they
decay dead plants and animals
WM iii
Oxygen is vital to living things. In a lake, there must be a
balance between oxygen added and oxygen used.
50
Unit 1
vinegar
lemon juice
car battery acid
Pure Substances and Mixtures
51
SKILLS MENU
• Questioning
• Hypothesizing
OPlanning
• Conducting
• Recording
• Analyzing
• Communicating
Making Connections
1. Most manufacturers of hair
shampoo say that their
product is not affected by the
hardness of water. How could
you prove or disprove this
claim? Design a procedure
and, with your teacher's
permission, carry it out.
How Hard Is the Water?
Hard water forms when certain substances, such as calcium and
magnesium, dissolve in it, as shown in Figure 1. One of the properties
of hard water is that soap does not lather very well in it. However, hard
water tastes better, unless it contains dissolved sulfur, and is better for
you because of its mineral content.
Question
® D Read this investigation. What question is it attempting
to answer?
Hypothesis
® El Create a hypothesis for this investigation.
Materials
•
•
•
•
•
•
•
•
•
apron
safety goggles
distilled water
1-L container
liquid soap
5-ml spoon
ruler
tap water
Epsom salts
Experimental Design
After adding known amounts of magnesium sulfate (also called Epsom
salts) to water, you will measure changes in the amount oflather
produced.
(a) Based on your
observations, what do you
suspect rs aiff erent in the
ingredients of liquid soap
and shampoo? Explain.
Check the labels on some
containers to verify your
answer.
m the rain water.
making it hard.
Exploring
iifiiihil
Rain water, which rs naturally soft, becomes hard as it runs
over and through rocks and soil.
Procedure
2. Design a procedure to
compare the hardness of local
)FJ water samples from the
school fountain, your home. a
local stream or nver, rain
water, etc. You can use the
graph you created in this
investigation to compare the
samples. Have your procedure
approved by your teacher
before you do any testing.
Analysis
II Place 250 mL of distilled
water in a 1-L container.
• Add 2 drops of liquid soap
and stir thoroughly.
• Quickly measure the
maximum height of the
layer of suds on the
surface.
~ (a) Record the height of
the layer of suds.
IJ Thoroughly rinse and dry
the container before
refilling it with another
250 mL of distilled water.
• Stir in 5 mL of Epsom salt
crystals until they have all
dissolved.
• Add 2 drops of liquid
soap, stir thoroughly, and
measure the height of the
suds.
El Repeat step 3 with fresh
distilled water and· 10 mL
of Epsom salts.
~ (a) Record the maximum
height of the layer of
suds.
~ (a) Record the maximum
height of the layer of
suds. Are the suds
higher or lower than
in step 1?
52 Unit 1
SKILLS HANDBOOK:
@ Asking a Question @ Predicting and Hypothesizing
(I
Continue this process,
adding an additional
5 mL of Epsom salts each
time, until no suds appear
on the surface of the
water, even after thorough
stirring. Clean up any
spills immediately.
'(a)
Record the maximum
height of the suds
each time.
(b) Describe the final
contents of the beaker.
II Analyzeyour results by answering
these questions.
]
(a) Use your data to draw a graph
comparing the height of the layer
of suds with the amount of Epsom
salts added.
(b) Based on your graph, explain the
relationship between the height of
the lather and the amount of
Epsom salts you added to your
solution.
(c) What effect does Epsom salts have
on water?
( d) Describe two observable
characteristics of hard water.
@constructing
Graphs
@ Testing and Evaluating a Prototype
Pure Substances and Mixtures
53
.
i
.
1.18
poison
flammable
Household Hazardous Waste
explosive
-~·
corrosive
Understanding Concepts
1. What does the term "hazardous
product" mean?
Making Connections
Do you contribute to water pollution like the people shown in
Figure 1? You may not think so, but we all use many solvents and
solutions at home because they help with cleaning, polishing, painting,
and other activities.These hazardous products often require special
handling and storage because they are dangerous to human health or
to the environment. Labels on these products indicate how they are
dangerous, as shown in Figure 2.
A second type of labelling, shown in Figure 3, gives detailed
information on the safe handling of a much wider variety of chemical
products. These are often found in the workplace, as well as in schools.
2. If methods of hazardous waste
disposal are inadequate in your
community, as a class, prepare
recommendations on how disposal
methods could be improved and
forward them to local officials.
Reflecting
3. Some people believe that one way
to solve pollution is to flush
poisonous chemicals down the
drain. What would you tell them?
WMiiJ
Government regulations require that hazardous household
products must be marked with warning symbols that indicate
why, and to what degree, a product is dangerous.
~
compressed
'e::.,,J
gas
@
flammable and
combustible
material
@
··@.}
~":'~
~
dang~rously
reactive
material
biohazardous
infectious
material
@
oxidiz(ng
material
t;;:::;;:,.,
corrosive
®
(I)
~material
poisonous
and infectious
~aterial causing
immediate
and serious
toxic effects
poisonous
and lnfectious
material
causing
other toxic
effects
D.esign Challenge
A recycling program
may gather containers
that hold hazardous
products. How can you
make the process safe
for environment
workers?
Util'liil
·W
WMlll
community waste
water stream
54
Unit 1
A small amount of hazardous
substances poured into the sewage
system from every home can add
up to a lot of pollution.
Labels from the Workplace Hazardous Materials Information
System (WHMIS). Before using any products, always read the
label to check how to handle the product safely.
Solutions for Hazardous Products
Municipal sewage treatment plants are not
designed to handle hazardous products, because
of the difficulty of separating them from waste
water. Neither are most landfill sites equipped to
deal with hazardous wastes.
• In many communities you can take your
hazardous materials to special collection
depots. From there they are taken to
incinerators that destroy them at high
temperatures. Some substances, such as motor
oil and paint thinners, can be cleaned and
reused.
• It is important to buy only the amount of
material that you need, so you don't have
much remaining to throw away.
• In some instances there are safer products
that can do the same job.
How Is Waste Disposed of in Your Community?
Everyone has different types of hazardous
wastesin their homes. Are they being
disposed of correctly?
1. What have you and your family been
•
•
Create a list of hazardous products in
your home. Do not open containers.
Check each room, including the garage
and bathroom. Beside each item,
indicate whether it belongs in one of the
four categories of household hazards
listed in Figure 2.
SKILLS HANDBOOK: (4A) Research Skills
doing with your "almost empty"
containers of hazardous waste?
Find out how hazardous wastes are
collected and disposed of in your
community.
2. How do you dispose of the products
listed?
:4A)
3. Prepare an action plan for your family to
dispose of hazardous waste.
Pure Substances and Mixtures
55
I
I
1.19
Explore an Issue
Cleaning Up Our Water
You've learned that many substances dissolve in water. Unfortunately,
this has resulted in pollution of many of our water systems, as people
dump waste into lakes and streams.
The major source of water in Ontario, the Great Lakes, is the
dumping ground for many pollutants from both sides of the border.
This has been a problem for decades, as many Canadian and American
cities and their industries are located on the shores of the Great Lakes.
Thunder Bay, Sault Ste. Marie, Chicago, Windsor, Detroit, Buffalo,
Hamilton ... the list is long.
About 5800 t of pollutants are added each year. Most of the
industrial waste is added to Lake Erie ( 40%) and Lake Michigan
(28%). Less of the total is dumped into Lake Ontario (_19%),and the
least is added to Lake Superior (7%) and Lake Huron (6%).
~easuring the Problem
Scientists on both sides of the border are
trying to learn more about each of the
vast amount of chemicals that has been
dumped or washed into the huge
chemical solution that fills the Great
Lakes. Of course, that chemical solution
is also the source of drinking water for
millions of people. There are many
questions that these scientists must
answer. For example, many chemicals are
dangerous only when they reach a certain
concentration. But what is the dangerous
concentration for each chemical? What
are the sources of the chemicals? How
can we reduce the amount of these
chemicals that enter the lakes?
This research, along with increasing
public awareness, is gradually resulting in
a reduction in the amount of waste being
dumped into the Great Lakes (Figure 1).
Although there have been significant
reductions in the amounts of municipal
and industrial waste being dumped into
the Great Lakes, many polluters still
remain.
56
Unit 1
Debate
Cleaning Up the Great Lakes
QIO
Statement
The Great Lakes have been a dumping ground for both industrial and
municipal (human) pollutants for hundreds of years. With adequate
treatment, water from the Great Lakes still remains safe for human
consumption. Appeals to reduce or eliminate pollutants at their source
are often countered with arguments about the economic consequences
of such initiatives. Can we continue to move at the present pace of
reduction and still be assured of a safe source of drinking water in the
next millennium and beyond?
Point
Counterpoint
• Companies and cities should
be permitted to dump some
waste into the Great Lakes.
Since the volume of water in
the lakes is so large, the waste
will be diluted to safe
concentrations.
•·The cost of waste treatment is
high. If companies based
around the Great Lakes are
forced to spend more money
on pollution control than
other companies located
elsewhere, products from the
Great Lakes area will cost
more. This could mean lost
sales and lost jobs.
• Even a small amount of some
pollutants can cause serious
effects. As the pollutants
accumulate through the food
chain, the concentration for
humans, at the end of the
chain, can become high
enough to be poisonous.
• Living things depend on clean
water. If the water in the Great
Lakes is polluted, all living
things suffer, including people.
People can find other jobs, but
damage to health and the
environment is difficult to fix.
What Do You Think7
WM iii
Pollution created by industry and our activities flows into the
Great Lakes. How far should we go in reducing that flow?
• Consider the statement and the points and counterpoints. Discuss.
What other points and counterpoints can you think of?
• Research the issue for both sides, using newspapers, a library
periodical index, a CD-ROMdirectory, or the Internet for
information on Great Lakes water pollution.
• Form a group to represent one side of the issue. Others in your class
will form a group to represent the other side.
• Conduct a debate defending each group's position.
SKILLS HANDBOOK: (so) Exploring an Issue
Pure Substances and Mixtures
57
Wetlands Preservation
''Hip
waders, binoculars, compass, and
bug spray are some of the tools of
my trade. My name isJoannaJohn
and I am a wetlands specialist with the Upper
Thames River Conservation Authority.
'Wetlands are more than just a haven for
wildlife. Other benefits, such as improving water
quality, decreasing downstream flooding,
increasing flow in a drought, and controlling soil erosion, are also important.
"I spend a lot of time in the Thames River watershed carrying out
evaluations of the wetlands. In the field, I take water samples and study the
direction of water movement, make lists of plants and animals that live there,
look for rare and endangered species, and note any disturbances by people.
"I work with the staff of the conservation authority and a variety of
community groups and individuals to develop management plans for the
wetlands. I also conduct hikes and prepare educational materials about the
importance of wetlands."
An Artificial Wetland
Sewage treatment plants generally do not have the capability of removing
household hazardous waste from sewage. Some cities are beginning to look
to nature, specificallywetlands, to see how nature cleans water.
Based on whatJoanna and her colleagues have learned about the
wetlands in the Thames River watershed, engineers working for the City of
London in Ontario have created Mornington Pond. Although it looks like a
natural wetland, as you can see in Figure 1, it is a carefully designed system
for controlling and purifying the huge amounts of water that collect during a
storm, when the city's sewage system would normally become overloaded.
Mornington Pond is actually a series of ponds. The ponds hold and clean
storm water until water flow to the sewage treatment plant returns to normal,
and water levels in the river go down. The water is then gradually released
into the Thames River in the same way that treated water from the sewage
plant is released.
As water collects in the ponds, heavier sediment particles, often carrying
contaminants, sink to the bottom, where they are periodically removed. More
than 1000 native plant species planted in the ponds help purify the water by
absorbing dissolved substances and controlling erosion in the same way that a
natural wetland functions.
Mornington Pond is an environmentally friendly, cost-effectiveway of
purifying water. So far, it has cost $3 million less than a traditional water
treatment facility.
58
Unit 1
WM iii
Mornington Pond is
an artificial wetland,
created by the City
of London. Wetlands
are rich
environments,
formed in areas
where water drains
slowly.
Round Table-Wetlands
In your community, a developer, a local
realtor, and the chamber of commerce are
proposing to develop a new shopping mall.
The mall promises to create 350 temporary
construction jobs the first year, followed by
500 permanentjobs in various mall stores.
The proposed site for the new mall
includes part of a wetlands area where many
plants and animals live. The wetlands have
also reduced flooding in the area over the
years. The land is privately owned.
•
List five arguments that might be used
to justify moving ahead with the project
as outlined.
•
List five arguments that might be put
forward to oppose the development.
•
Decide which of the 10 arguments is the
strongest and prepare to support the
argument in a round table discussion.
You may wish to contact local resource
people while doing your research.
SKILLS HANDBOOK:
@) Exploring an Issue
or a Mall?csn
•
Present your
information
and position
at the round
table,
individually or
as part of a
"pro" or "con" group.
1. Did your viewschange during research
and discussion of this issue? Explain.
2. Based on your research and the round
table discussion, list the factors that are
critical for deciding whether a wetland
or other habitat should be destroyed
when creating a new development.
3. Consider "sustainability."What
implications would there be on the
environment, the economy, society?
Pure Substances and Mixtures 59
UDMiil
Water Additives
You have discovered that there are many
substances dissolved in fresh water. After
learning about water pollution, you may be
wondering if all substances in the water are
unsafe. In fact, some substances are beneficial.
Iron, for example, is found naturally in water
that flows over limestone, and is a key
substance in hemoglobin, which carries
oxygen in your blood.
Chlorine and Our Water
Water treatment plants, like the one in
Figure 1, deliberately add substances to
drinking water, taking advantage of its
dissolvingproperties. Chlorine is dissolved in
both drinking water and swimmingpools for
the same reason-to destroy bacteria. In the
past, bacteria-containing water killed millions
of people by causing diseases such as cholera.
Chlorine is added to water supplies to
eliminate such bacteria.
Most people never give chlorinated water a
thought. However, scientific studies are
showing a link between chlorinated drinking
water and a variety of health effects. For
example, chlorinated water may destroy some
of the bacteria in our intestines that help us
digest our food. Also, excessiveamounts of
chlorine in swimming pools can aggravate
asthma in children.
Understanding Concepts
The bacteria that live in our
mouths can be a threat to teeth.
1. What is one benefit and one
drawback of dissolved chlorine in
water?
O
Fluoride and Our Water
Another chemical added to drinking water to
protect teeth is a compound that contains
fluoride. Several studies have indicated that
water fluoridation is a safe and cost-effective
means of reducing tooth decay, as shown in
Figure 2. For residents of communities that
don't have water fluoridation, the alternative
is regular visits to a dentist for fluoride rinses.
Since there is an alternative to fluoridating
all of our drinking water, some groups feel
that if there is a slight chance that fluoride
might be harmful, then it should not be
added to community water supplies. For
example, some research suggests that longterm use of flouride may be slowlydestroying
our bones, teeth, and general health. Too
much flouride can actually weaken teeth,
making them porous and easily stained. It
turns out that fish and other aquatic life don't
react well to the addition of fluoride at
higher-than-recommended levels.
Should we continue to add fluoride and
chlorine to drinking water? Are there safer
alternatives? If we continue, what is the
minimum amount of these substances that we
can add? Scientificallyaware citizens must ask
such questions to encourage study and ensure
that responsible decisions will be made.
Bacteria that feed on sugar in
the mouth produce acids.
2. Describe in your own words what
is meant by fluoridation and
chlorination.
3. Draw a comic strip describing the
life of a bacteria on your tooth.
4. State one risk in using
unchlorinated drinking water.
Making Connections
0
The acid produced by the
bacteria eats through tooth
enamel.
5. A thirsty hiker finds a stream in
the wilderness. She has special
water purification tablets in her
pack but decides not to use them,
since there are no houses or
industries in the area. Is she right
to drink the water untreated? Give
your reasons.
Exploring
G
(!)
Bacteria enter the tooth
through the hole in the enamel
and infect the tooth.
Fluoride compounds dissolved
in water enter the tooth enamel
and make it stronger.
6. Travellers to remote parts of the
world often carry small kits with
them that purify water. Find out
how one of these works. Where
else do you think similar types of
water purifiers might be useful?
7. Using electronic and print sources,
research the advantages and
disadvantages of adding flounde
to our drinking water. Present your
report to the class.
li@jijij•
Many municipalities have water treatment plants where solids
and dissolved substances are removed from the water to make
it drinkable. These plants also add chemicals for health
reasons.
O The tougher
0
enamel resists
bacterial acid.
O)sign Challenge
How large are bacteria?
Will your design for
purifying water remove
them?
Pure Substances and Mixtures
61
Your model will be assessed
according to how well you:
Design and Build a System
That Separates or Purifies Materials
Process
• Understand the problem
• Develop a safe plan
Reusing and recycling all sorts of substances and products, both liquid
and solid, has become ever more important as our growing population
uses more of Earth's resources and creates more garbage. Our mineral
resources are limited, and so is our supply of fresh, clean drinking
water. Purifying our water and separating different materials for reuse
requires many types of technology.
II
A Water Purification System
Problem Situation
Although people in cities have access to
purified water, those who live in rural and
more remote areas may take their water from
lakes and rivers, where the water is often
murky due to particles mixed in it.
Design Brief
• Design and build a filtering system that
removes solid particles from water.
Design Criteria
• The device must be able to remove
microscopic particles from the water
(verified with a microscope).
• The water must move through the filtering
system under pressure.
• Additional tests must be outlined for
establishing the safety of the water for
drinking.
II
lii\Miil
Carrots are sorted
mechanically by size
and then by visual
inspection.
-A Recycling System for Plastic,
Glass, Metal, and Paper
Problem Situation
Although many people separate the different
types of recyclablematerials before putting
them out on the curb, recyclingcompanies
must separate the substances more accurately
before they can be processed into new materials.
Design Brief
• Design a system in which a mixture of
plastic, glass, metal, and paper items are
separated from each other.
Design Criteria
• Each component (plastic, glass, metal,
paper} must be removed from the mixture
in a set sequence.
• The separation processes must be safe and
efficient.
• A flow chart outlining the system must
accompany the model.
iiiii'iiiJ
All the materials in
this yard can be
recycled, but they
must first be
separated from one
another.
• Choose and safely use
appropriate materials, tools,
and equipment
• Test and record results
II
A Mechanical Soil and Gravel
Separator
Problem Situation
Earth that is dug up often contains a mixture
of many different particle sizes, from tiny clay
particles to large pieces of gravel. However,
gardeners and landscapers need these
substances separated so that they are usable.
For example, the gravel is useful for driveways
or walkways;gardeners need clay to improve
sandy soil; and so on.
Design Brief
• Design and build a separating device that
efficiently separates the particles in stony
soil into three different sizes.
Design Criteria
• The separating device must be capable of
separating at least 1 kg of soil.
• The separator must collect each of the
three different-sized particles in separate
compartments.
• The separator must work without being
touched directly by a human operator.
• Evaluate your model,
including suggestions for
improvement
Communicate
• Prepare a presentation
• Use correct terms
• Write clear descriptions of the
steps you took in building
and testing your model
• Explain clearly how your
model solves the problem
• Make an accurate technical
drawing for your model
Produce
• Meet the design criteria with
your model
• Use your chosen materials
effectivelyand carefully
• Construct your model
• Solve the identified problem
A
U
When preparing to build or
test a design, have your plan
approved by your teacher
before you begin.
@Mill
Water is purified for drinking. The first step in this
process is to improve the clarity of the water.
62
Unit 1
Pure Substances and Mixtures
63
I
• evaluate the quality of water from different
sources by performing simple tests 1.16, 1.17,
1.21
• identify factors that affect the rate at which
a substance dissolves 1.4, 1.7, 1.14
• identify different types of waste present in
the community and the environmentally
acceptable methods for their disposal 1.14,
1.15, 1.18
y
Making Connections
• recognize that solutions in manufactured
products can exist as solids, liquids, and gases
1.1, 1.11, 1.12
• distinguish between raw materials and
manufactured products 1.12, 1.13
• identify a variety of manufactured products
made from mixtures and explain their
functions 1.6, 1.12, 1.13
• describe how raw materials are collected and
processed to produce a variety of products
1.12, 1.13
• identify the sources and characteristics of
pollutants that result from manufacturing
and agricultural processes 1.15, 1.19
Reflecting
• Reflect on the ideas and questions presented in
the Unit Overview and in the Getting Started.
• describe the effects of some toxic solvents on
the environment and regulations that ensure
their safe use and disposal 1.18
• identify solutes and solvents in various
kinds of solutions 1.1, 1.11, 1.12
• demonstrate the use of water as a solvent and
as a chemical reactant 1,1, 1.4, 1.6, 1.10, 1.13,
1.14, 1.15, 1.17, 1.21
Applying Skills
• evaluate how human use of natural resources
has affected water systems 1.4, 1.17
How can you connect what you have done and
learned in this unit with those ideas and
questions? (To review, check the sections
indicated in this Summary.)
• Revise your answers to the Reflecting questions
inG,@, ~ and the questions you created in the
Getting Started. How has your thinking changed?
• What new questions do you have? How will
you answer them?
Understanding Concepts
• distinguish between pure substances,
mechanical mixtures, and solutions using
the particle theory 1.1, 1.2
• use the particle theory to explain how
substances dissolve, based on attractions
between the particles of solute and solvent
1.2, 1.5
• describe the difference between saturated
and unsaturated solutions, between dilute
and concentrated solutions 1.8, 1.9
64
Unit 1
• classifya sample of matter as a pure
substance or a mixture; as a solution or
a mechanical mixture 1.1, 1.2 y
• conduct
experiments to
determine various
factors that affect
the rate at which
substances dissolve
1.4, 1.7, 1.14
• determine the
amount of solute
required to form a
saturated solution
with a fixed amount
of solvent at various
temperatures 1.9
• investigate different
methods of
separating the
components of
mixtures 1.3, 1.10, 1.20
• understand and use the following terms:
alloy
ceramic
concentrated solutions
dilute solutions
glass
hard water
hazardous product
heterogeneous mixture
homogeneous mixture
matter
mechanical mixture
mixture
particle theory
pH scale
plastic
pure substance
raw material
saturated solutions
soft water
solubility
solute
solution
solvent
supersaturated
turbidity
unsaturated solutions
WHMIS
Pure Substances and Mixtures
65
I
11. Identify a solute and the solvent in each of
the following solutions:
Understanding Concepts
1. Copy the terms in Column A into your
notebook. Match each term with the most
correct description from Column B.
Column A
mechanical mixture
solvent
solute
concentration
dissolve
insoluble
dilute
saturated
unsaturated
soluble
ColumnB
a solute that "disappears" in a solvent
mix together very well
a tiny bit of solute in a large amount of solvent
contains more dissolved material than is
required for saturation. at that temperature
something in which a substance dissolves
the mass of dissolved material in a
specified amount of solvent
all spaces between solvent particles filled with
solute
two or more pure substances in the
same container
the substance that gets dissolved
mix together very well
2. State, with a reason, whether each of the
following is a solution or a mechanical
mixture:
6. How do each of the following affect the
solubility of a solid solute in water?
(c) brass
(b) stirring
(d) steel
7. The Moon was once believed to have no
water anywhere on its surface.Jf this were
true, could there be solutions on the
Moon? Explain.
8. Read the following statements. Rewrite
those that are incorrect so that they
become correct.
(a) If a solution is saturated at 20°C, it will
also be saturated at 25°C.
(b) When some solvent evaporates, a
solution becomes more saturated.
(c) When a saturated solution is cooled,
some crystals begin to appear in the
solution. The solution is now
unsaturated.
( d) A solvent is a liquid that dissolves sugar.
( e) A solute is alwaysa solid.
(b) freshly squeezed grapefruit juice
(f) Dissolving means mixing two things
together.
(d) apple juice
(e) granola
(f) vegetable soup
3. Decide whether each of the following is a
solution or not. Give reasons for your choice.
(a) a mixture of clay and water
(b) a mixture of salt and water
(c) tomato juice
4. Give examples of the following:
(a) two pure substances
(b) two solid solutions
(c) two liquid solutions that do not contain
water
(d)a solution that is a gas
(b) air
(a) temperature
(a) hotdog relish
( c) soda water
(a) salt water
(g) Oil is insoluble.
9. Describe the information that you would
obtain from each of the labels below
(a)
~
(b)
I"
(c)
ti&
~
10. Use the particle theory to explain
(a) the difference between a pure substance
and a mixture
(b) the difference between a solution and a
mechanical mixture
( c) how a small amount of sugar dissolves in
a container of water.
12. What is the ideal pH for fresh water? Why?
What is the effect on fresh water organisms
if the water becomes too acidic? How are
some bodies of water able to offset acidic
precipitation? Explain your answers.
13. Why are each of the following added to
drinking water?
blue liquid in a shallow container. We
placed it on the windowsill over the
weekend. On Monday morning, there was
no liquid left, but the dish had some solid
blue stuff in it."
(a) Was the blue liquid in the dish a
heterogeneous mixture, a solution, or a
pure substance? Design a procedure to
verify your choice.
(b) Write a hypothesis to account for what
happened in the dish.
19. Use the solubility data for solid potassium
nitrate in water at various temperatures
from Table 1. Graph the data and answer
the following questions.
(a) chlorine
(b) fluoride
14. What does the term "hazardous" mean
when it is used to describe a substance? You
dump a small amount of paint thinner
down the drain before putting the can at
the curb for recycling. Are you being
environmentally responsible? State your
reasons.
15. You add one teaspoon of lemon juice to a
400-mL cup of water. A friend adds four
teaspoons of lemon juice to her 400-mL
cup of water. Into whose cup would more
sugar need to be added to make the drink
sweet? Explain.
16. A perfume chemist determines that 5 g of
Brand X perfume can dissolve in 50 g of
water at room temperature. She also finds
that 10 g of Brand Y perfume can dissolve
in 100 g of water. She concludes that Brand
Y perfume is more soluble in water than
Brand X. Do you agree with her findings?
Explain.
Applying Skills
17. Using a flashlight, how can you distinguish
between a solution and a mechanical
mixture?
18. Prakesh ·makes the following entry in her
notebook: "On Friday we were given a clear
IEWll
Temperature (°C)
0
10
20
30
40
50
60
Solubility of potassium nitrate
(g solute/1009 water)
14
21
31
45
60
85
110
(a) How many grams of potassium nitrate
will dissolve in 100 g of water at 30°C?
At 35°C?
(b) At what temperature will 40 g of
potassium nitrate dissolve in 100 g of
water to form a saturated solution?
(c) At what temperature will 85 g of
potassium nitrate dissolve in 100 g of
water to form a saturated solution?
(d) If 30 g of potassium nitrate are dissolved
in 100 g of water at 18°C, is the solution
saturated? Explain.
20. Use the data provided in Table 1 in 1.8 to
draw the solubility graphs for both sugar
and salt. Use the graphs to answer the
following questions.
(a)How much sugar will dissolve to form a
saturated solution in 100 g of water at
60°C? Salt?
(b)lf 20 g of salt is completely dissolved in
100 g of water at 50°C, what kind of
solution will result?
5. Is an alloy a pure substance or a mixture?
Use the particle theory to explain your
answer.
66
Unit 1
Pure Substances and Mixtures
67
21. Genna decides that, while she brushes her
teeth, the tap should only be running while
the toothbrush is being rinsed. She decides
to investigate how much water is used if the
tap is left running all the time she brushes.
To her surprise, the extra water fills one
1.75-L bottle, along with half of another. If
she brushes three times daily, how much
water will Genna save in a year by turning
off the tap?
22. A laboratory receives a bottle of red liquid
for analysis. After it sits overnight, bits of
red powder are found on the bottom of the
container. When lab technicians shine a
light into the container, the top of the
beam appears pink, while the bottom
appears red. Tiny particles are also
observed in the beam of light. Does this
bottle contain a solution? Explain.
23. Suggest a method to separate each of the
following mixtures:
(a) sand, salt, and bird seed
(b) sugar, flour, and pennies
( c) water and salad oil
( d) iron powder, salt, and iron nails
24. Michael's results in a dissolving
investigation are not consistent with the
results of other students in the class. For
solute l, Michael half-filled a test tube with
tap water, put in some solute, and then
shook the test tube until his arm got tired.
For solute 2, he put 5 mL of water into a
beaker, added two crystals of solute 2, and
stirred the contents once or twice with a stir
stick.
(a) What would you suggest to Michael to
improve his experimental technique?
(b) Effram and Michael argued over solute
3. Effram described it as "not very
soluble." Michael insisted that it is
"insoluble." How might you determine
who is right?
25. Water is used to deliver fluoride to the
citizens of a community because it is an
excellent "carrier." What makes water such
a good carrier?
68
Unit 1
Making Connections
26. Why does air, a solution, feel much more
humid on a hot day than on a cool one,
even if the relative humidity on both days is
the same?
27. A good angel food cake does not appear to
have any icing. Your grandmother tells you
that she sprinkled some powdered sugar on
the moist cake when it came out ofthe
oven. What happened to it?
28. A student carefully removes the cap from a
chilled bottle of pop. The open top is
covered with a balloon that is secured with
tape. When she shakes the bottle, the
balloon fills with gas. This sequence is
repeated with an identical bottle of pop at
room temperature.
(a) Which balloon will fill with the greatest
amount of gas? Explain.
(b) How is the solubility of carbon dioxide
gas related to the temperature of the
beverage?
29. Galvanized nails are now used for most
outdoor applications. Investigate how a
metal is galvanized and determine whether
galvanized nails are, in fact, an alloy.
30. Gases that dissolve in water can make it
look cloudy. Will hot water or cold water
likely produce a cloudy ice cube? Explain.
31. Laura observes her friend Ingrid preparing
to make a glass of lemon iced tea from a
drink mix. Ingrid first fills a tall glass with
ice cubes. She then adds a spoonful of
drink mix and two sugar cube to the glass
before adding cold tap water. A
considerable amount of undissolved solid
remains at the bottom of the glass.
(a) Describe four suggestions that Laura
could make to reduce the amount of
undissolved solid.
(b) Is Ingrid's first drink saturated,
unsaturated, or supersaturated? Explain.
(c) If Laura's suggestions are taken and
there is no evidence of undissolved solid
in the glass, how would you now
describe the drink?
32, If pure gold is described as 24 karat, then
18-karat gold must consist of 18 parts gold
and 6 parts other metals, such as copper.
(a) Name the solute in 18-karat gold.
(b) Name the solvent.
(c) Bill's girlfriend gives him
a pure gold chain for his
.birthday. After a few
weeks of wearing it, his
skin becomes discoloured
under the chain. What advice would you
give Bill?
33, Rock candy is made by
dissolving sugar in
warm water to form a
saturated solution
and then is allowed to
cool.
(a) What is rock candy?
(b) Explain how it is formed based on what
you know about saturated solutions.
34. Imagine that you are an industrial chemist.
Part of your job is to think of new and
useful mixtures that your company can
make. Using the _followinglist of substances
and their properties, name three mixtures
that you would make, inventing a use for
each one.
Substance
Useful Property
A
sticks to plastic
B
is bright blue
c
boils at 20°C
D
smells like bananas
E
is elastic
F
glows in the dark
G
conducts electricity
H
bends without breaking
repels insects
35.Theinstructionson
an aerosol can of
oven cleaner advises
the user to wear
rubber gloves while
using the product.
The can also contains
two WHMIS warning
labels. Which two?
36. You decide to enter a competition to build
a mountain bike that has no metal parts.
(a) What materials that you have learned
about here would you use to replace the
metal parts of your mountain bike?
Explain the reasons for your choices.
(b) If you wanted to build a racing bike,
would your choice of materials change?
Explain.
37. Lake trout prefer oxygen-rich water. Where
would you expect to find trout in midsummer-at the bottom of the lake or near
the surface?
38. A soup recipe calls for the addition of
bouillon. A cook finds both bouillon
powder and bouillon cubes in the spice
cabinet. Which form of the substance will
speed up the process of making the soup?
39. A large bottle of liquid laundry detergent
states that it contains enough detergent to
wash 100 loads of laundry. A different
brand in a smaller bottle also states that it
contains enough detergent to wash 100
loads of laundry. Both are true. Explain
how this could be.
40. It is discovered that a newly developed
chemical reduces the desire to eat.
Politicians in a small municipality decide
that it would be a good idea to add small
amounts of this chemical to drinking water.
They argue that dissolving the chemical in
everyone's drinking water would result in a
lowered demand on countries to produce
food and would help overweight people
lose weight. State your position on this
issue. Give some reasons to support your
position.
Pure Substances and Mixtures
69